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Streams
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<H3 CLASS="subsection"><A NAME="htoc105">7.10</A>&nbsp;&nbsp;Streams</H3><UL>
<LI><A HREF="gprolog033.html#toc74">Introduction</A>
<LI><A HREF="gprolog033.html#toc75"><TT>current_input/1</TT></A>
<LI><A HREF="gprolog033.html#toc76"><TT>current_output/1</TT></A>
<LI><A HREF="gprolog033.html#toc77"><TT>set_input/1</TT></A>
<LI><A HREF="gprolog033.html#toc78"><TT>set_output/1</TT></A>
<LI><A HREF="gprolog033.html#toc79"><TT>open/4</TT>,
 <TT>open/3</TT></A>
<LI><A HREF="gprolog033.html#toc80"><TT>close/2</TT>,
 <TT>close/1</TT></A>
<LI><A HREF="gprolog033.html#toc81"><TT>flush_output/1</TT>,
 <TT>flush_output/0</TT></A>
<LI><A HREF="gprolog033.html#toc82"><TT>current_stream/1</TT></A>
<LI><A HREF="gprolog033.html#toc83"><TT>stream_property/2</TT></A>
<LI><A HREF="gprolog033.html#toc84"><TT>at_end_of_stream/1</TT>,
 <TT>at_end_of_stream/0</TT></A>
<LI><A HREF="gprolog033.html#toc85"><TT>stream_position/2</TT></A>
<LI><A HREF="gprolog033.html#toc86"><TT>set_stream_position/2</TT></A>
<LI><A HREF="gprolog033.html#toc87"><TT>seek/4</TT></A>
<LI><A HREF="gprolog033.html#toc88"><TT>character_count/2</TT></A>
<LI><A HREF="gprolog033.html#toc89"><TT>line_count/2</TT></A>
<LI><A HREF="gprolog033.html#toc90"><TT>line_position/2</TT></A>
<LI><A HREF="gprolog033.html#toc91"><TT>stream_line_column/3</TT></A>
<LI><A HREF="gprolog033.html#toc92"><TT>set_stream_line_column/3</TT></A>
<LI><A HREF="gprolog033.html#toc93"><TT>add_stream_alias/2</TT></A>
<LI><A HREF="gprolog033.html#toc94"><TT>current_alias/2</TT></A>
<LI><A HREF="gprolog033.html#toc95"><TT>add_stream_mirror/2</TT></A>
<LI><A HREF="gprolog033.html#toc96"><TT>remove_stream_mirror/2</TT></A>
<LI><A HREF="gprolog033.html#toc97"><TT>current_mirror/2</TT></A>
<LI><A HREF="gprolog033.html#toc98"><TT>set_stream_type/2</TT></A>
<LI><A HREF="gprolog033.html#toc99"><TT>set_stream_eof_action/2</TT></A>
<LI><A HREF="gprolog033.html#toc100"><TT>set_stream_buffering/2</TT></A>
</UL>

<A NAME="Streams"></A>
<A NAME="toc74"></A>
<H4 CLASS="subsubsection"><A NAME="htoc106">7.10.1</A>&nbsp;&nbsp;Introduction</H4>
<A NAME="Introduction:(Streams)"></A>
A stream provides a logical view of a source/sink.<BR>
<BR>
<B>Sources and sinks</B>: a program can output results to a sink or input
data from a source. A source/sink may be a file (regular file, terminal,
device,...), a constant term, a pipe, a socket,...<BR>
<BR>
<B>Associating a stream to a source/sink</B>: to manipulate a source/sink
it must be associated with a stream. This provides a logical and uniform view
of the source/sink whatever its type. Once this association has been
established, i.e. a stream has been created, all subsequent references to
the source/sink are made by referring the stream. A stream is
unidirectional: it is either an input stream or an output stream. For a
classical file, the association is done by opening the file (whose name is
specified as an atom) with the <TT>open/4</TT> (section&nbsp;<A HREF="#open/4">7.10.6</A>). GNU Prolog
makes it possible to treat a Prolog constant term as a source/sink and
provides built-in predicates to associate a stream to such a term
(section&nbsp;<A HREF="gprolog034.html#Constant-term-streams">7.11</A>). GNU Prolog provides operating system interface
predicates defining pipes between GNU Prolog and child processes with streams
associated with these pipes, e.g. <TT>popen/3</TT> (section&nbsp;<A HREF="gprolog050.html#popen/3">7.27.21</A>).
Similarly, socket interface predicates associate streams to a socket to
allow the communication, e.g. <TT>socket_connect/4</TT>
(section&nbsp;<A HREF="gprolog051.html#socket-connect/4">7.28.5</A>).<BR>
<BR>
<B>Stream-term</B>: a stream-term identifies a stream during a call of an
input/output built-in predicate. It is created as a result of associating a
stream to a source/sink (section above). A stream-term is a compound term of
the form <TT>'$stream'(I)</TT> where <TT>I</TT> is an integer.<BR>
<BR>
<B>Stream aliases</B>: any stream may be associated with a stream alias
which is an atom which may be used to refer to that stream. The association
can be done at open time or using <TT>add_stream_alias/2</TT>
(section&nbsp;<A HREF="#add-stream-alias/2">7.10.20</A>). Such an association automatically ends when the
stream is closed. A particular alias only refers to at most one stream at any
one time. However, more than one alias can be associated with a stream. Most
built-in predicates which have a stream-term as an input argument also accept
a stream alias as that argument. However, built-in predicates which return a
stream-term do not accept a stream alias.<BR>
<BR>
<B>Standard streams</B>: two streams are predefined and open during the
execution of every goal: the standard input stream which has the alias
<TT>user_input</TT> and the standard output stream which has the alias
<TT>user_output</TT>. A goal which attempts to close either standard stream
succeeds, but does not close the stream.<BR>
<BR>
<B>Current streams</B>: during execution there is a current input stream
and a current output stream. By default, the current input and output
streams are the standard input and output streams, but the built-in
predicates <TT>set_input/1</TT> (section&nbsp;<A HREF="#set-input/1">7.10.4</A>) and
<TT>set_output/1</TT> (section&nbsp;<A HREF="#set-output/1">7.10.5</A>) can be used to change them.
When the current input stream is closed, the standard input stream becomes
the current input stream. When the current output stream is closed, the
standard output stream becomes the current output stream. <BR>
<BR>
<B>Text streams and binary streams</B>: a text stream is a sequence of
characters. A text stream is also regarded as a sequence of lines where each
line is a possibly empty sequence of characters followed by a new line
character. GNU Prolog may add or remove space characters at the ends of lines
in order to conform to the conventions for representing text streams in the
operating system. A binary stream is a sequence of bytes. Only a few
built-in predicates can deal with binary streams, e.g.
<TT>get_byte/2</TT> (section&nbsp;<A HREF="gprolog036.html#Byte-input/output">7.13</A>).<BR>
<BR>
<B>Stream positions</B>: the stream position of a stream identifies an
absolute position of the source/sink to which the stream is connected and
defines where in the source/sink the next input or output will take place. A
stream position is a ground term of the form
<TT>'$stream_position'(I1, I2, I3, I4)</TT> where <TT>I1</TT>,
<TT>I2</TT>, <TT>I3</TT> and <TT>I4</TT> are integers. Stream positions are
used to reposition a stream (when possible) using for instance
<TT>set_stream_position/2</TT> (section&nbsp;<A HREF="#set-stream-position/2">7.10.13</A>).<BR>
<BR>
<B>The position end of stream</B>: when all data of a stream
<I><TT>S</TT></I> has been input <I><TT>S</TT></I> has a stream position
end-of-stream. At this stream position a goal to input more data will return
a specific value to indicate that end of stream has been reached (e.g.
<TT>-1</TT> for <TT>get_code/2</TT> or <TT>end_of_file</TT> for
<TT>get_char/2</TT>,...). When this terminating value has been input, the
stream has a stream position past-end-of-stream.<BR>
<BR>
<B>Buffering mode</B>: input/output on a stream can be buffered
(line-buffered or block-buffered) or not buffered at all. The buffering mode
can be specified at open time or using <TT>set_stream_buffering/2</TT>
(section&nbsp;<A HREF="#set-stream-buffering/2">7.10.27</A>). Line buffering is used on output streams,
output data are only written to the sink when a new-line character is output
(or at the close time). Block buffering is used on input or output. On input
streams, when an input is requested on the source, if the buffer is empty,
all available characters are read (within the limits of the size of the
buffer), subsequent reads will first use the characters in the buffer. On
output streams, output data are stored in the buffer and only when the
buffer is full is it physically written on the sink. Thus, an output to a
buffered stream may not be sent immediately to the sink connected to that
stream. When it is necessary to be certain that output has been delivered,
the built-in predicate <TT>flush_output/1</TT> (section&nbsp;<A HREF="#flush-output/1">7.10.8</A>)
should be used. Finally, it is also possible to use non-buffered streams, in
that case input/output are directly done on the connected source/sink. This
can be useful for communication purposes (e.g. sockets) or when a precise
control is needed, e.g. <TT>select/5</TT> (section&nbsp;<A HREF="gprolog050.html#wait/2">7.27.25</A>).<BR>
<BR>
<B>Stream mirrors</B>: any stream may be associated with mirror streams
specified at open time or using <TT>add_stream_mirror/2</TT>
(section&nbsp;<A HREF="#add-stream-mirror/2">7.10.22</A>). Then, all characters/bytes read from/written to
the stream are also written on each mirror stream. The association
automatically ends when either the stream or the mirror stream is closed. It
is also possible to explicitely remove a mirror stream using
<TT>remove_stream_mirror/2</TT>
(section&nbsp;<A HREF="#remove-stream-mirror/2">7.10.23</A>).<BR>
<BR>
<A NAME="toc75"></A>
<H4 CLASS="subsubsection"><A NAME="htoc107">7.10.2</A>&nbsp;&nbsp;<TT>current_input/1</TT></H4>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
current_input(?stream)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>current_input(Stream)</TT> unifies <TT>Stream</TT> with the stream-term
identifying the current input stream.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Stream</TT> is neither a variable nor a stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream, Stream)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicate.<BR>
<BR>
<A NAME="toc76"></A>
<H4 CLASS="subsubsection"><A NAME="htoc108">7.10.3</A>&nbsp;&nbsp;<TT>current_output/1</TT></H4>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
current_output(?stream)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>current_output(Stream)</TT> unifies <TT>Stream</TT> with the
stream-term identifying the current output stream.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Stream</TT> is neither a variable nor a stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream, Stream)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicate.<BR>
<BR>
<A NAME="toc77"></A>
<H4 CLASS="subsubsection"><A NAME="htoc109">7.10.4</A>&nbsp;&nbsp;<TT>set_input/1</TT></H4>
<A NAME="set-input/1"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
set_input(+stream_or_alias)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>set_input(SorA)</TT> sets the current input stream to be the stream
associated with the stream-term or alias <TT>SorA</TT>.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is an output stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(input, stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicate.<BR>
<BR>
<A NAME="toc78"></A>
<H4 CLASS="subsubsection"><A NAME="htoc110">7.10.5</A>&nbsp;&nbsp;<TT>set_output/1</TT></H4>
<A NAME="set-output/1"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
set_output(+stream_or_alias)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>set_output(SorA)</TT> sets the current output stream to be the stream
associated with the stream-term or alias <TT>SorA</TT>.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is an input stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(output, stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicate.<BR>
<BR>
<A NAME="toc79"></A>
<H4 CLASS="subsubsection"><A NAME="htoc111">7.10.6</A>&nbsp;&nbsp;<TT>open/4</TT>,
 <TT>open/3</TT></H4>
<A NAME="open/4"></A>
 
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
open(+source_sink, +io_mode, -stream, +stream_option_list)<BR>
open(+source_sink, +io_mode, -stream)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>open(SourceSink, Mode, Stream, Options)</TT> opens the source/sink
<TT>SourceSink</TT> for input or output as indicated by <TT>Mode</TT> and
the list of stream-options <TT>Options</TT> and unifies <TT>Stream</TT> with
the stream-term which is associated with this stream. See
<TT>absolute_file_name/2</TT> for information about the syntax of
<TT>SourceSink</TT> (section&nbsp;<A HREF="gprolog049.html#absolute-file-name/2">7.26.1</A>).<BR>
<BR>
<B>Input/output modes</B>: <TT>Mode</TT> is an atom which defines the
input/output operations that may be performed the stream. Possible modes
are:
<UL CLASS="itemize"><LI CLASS="li-itemize"><TT>read</TT>: the source/sink is a source and must already exist.
Input starts at the beginning of the source. <BR>
<BR>
<LI CLASS="li-itemize"><TT>write</TT>: the source/sink is a sink. If the sink already exists
then it is emptied else an empty sink is created. Output starts at the
beginning of that sink.<BR>
<BR>
<LI CLASS="li-itemize"><TT>append</TT>: the source/sink is a sink. If the sink does not exist
it is created. Output starts at the end of that sink.</UL>
<B>Stream options</B>: <TT>Options</TT> is a list of stream options. If
this list contains contradictory options, the rightmost option is the one
which applies. Possible options are:
<UL CLASS="itemize"><LI CLASS="li-itemize"><TT>type(text</TT>/<TT>binary)</TT>: specifies whether the
stream is a text stream or a binary stream. The default value is
<TT>text</TT>.<BR>
<BR>
<LI CLASS="li-itemize"><TT>reposition(true</TT>/<TT>false)</TT>: specifies
whether it is possible to reposition the stream. The default value is
<TT>true</TT> except if the stream cannot be repositioned (e.g. a terminal).<BR>
<BR>
<LI CLASS="li-itemize"><TT>eof_action(error</TT>/<TT>eof_code</TT>/<TT>reset)</TT>:
specifies the effect of attempting to input from a stream whose stream
position is past-end-of-stream:
<UL CLASS="itemize"><LI CLASS="li-itemize"><TT>error</TT>: a <TT>permission_error</TT> is raised signifying that
no more input exists in this stream.<BR>
<BR>
<LI CLASS="li-itemize"><TT>eof_code</TT>: the result of input is as if the stream position
is end-of-stream.<BR>
<BR>
<LI CLASS="li-itemize"><TT>reset</TT>: the stream position is reset so that it is not
past-end-of-stream, and another attempt is made to input from it (this is
useful when inputting from a terminal).</UL><BR>
The default value is <TT>eof_code</TT>.<BR>
<BR>
<LI CLASS="li-itemize"><TT>alias(Alias)</TT>: specifies that the atom <TT>Alias</TT>
is to be an alias for the stream. By default no alias is attached to the
stream. Several aliases can be defined for a same stream.<BR>
<BR>
<LI CLASS="li-itemize"><TT>mirror(Mirror)</TT>: specifies the stream associated with
the stream-term or alias <TT>Mirror</TT> is a mirror for the stream. By
default no mirro is attached to the stream. Several mirrors can be defined
for a same stream.<BR>
<BR>
<LI CLASS="li-itemize"><TT>buffering(none</TT>/<TT>line</TT>/<TT>block)</TT>:
specifies which type of buffering is used by input/output operations on
this stream:
<UL CLASS="itemize"><LI CLASS="li-itemize"><TT>none</TT>: no buffering.<BR>
<BR>
<LI CLASS="li-itemize"><TT>line</TT>: output operations buffer data emitted until a new-line
occurs<BR>
<BR>
<LI CLASS="li-itemize"><TT>block</TT>: input/output operations buffer data until a given
number (implementation dependant) of characters/bytes have been treated.</UL><BR>
The default value is <TT>line</TT> for a terminal (TTY), <TT>block</TT>
otherwise.</UL>
<TT>open(SourceSink, Mode, Stream, Options)</TT> is equivalent to
<TT>open(SourceSink, Mode, Stream, [])</TT>.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SourceSink</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mode</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Options</TT> is a partial list or a list with an element
<TT>E</TT> which is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mode</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, Mode)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Options</TT> is neither a partial list nor a list</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(list, Options)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Stream</TT> is not a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(variable, Stream)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SourceSink</TT> is neither a variable nor a source/sink</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(source_sink, SourceSink)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mode</TT> is an atom but not an input/output mode</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(io_mode, Mode)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>an element <TT>E</TT> of the <TT>Options</TT> list is neither a
variable nor a stream-option</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_option, E)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>the source/sink specified by <TT>SourceSink</TT> does not exist</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(source_sink, SourceSink)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>the source/sink specified by <TT>SourceSink</TT> cannot be opened</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(open, source_sink, SourceSink)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>an element <TT>E</TT> of the <TT>Options</TT> list is
<TT>alias(A)</TT> and <TT>A</TT> is already associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(open, source_sink, alias(A))</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>an element <TT>E</TT> of the <TT>Options</TT> list is
<TT>mirror(M)</TT> and <TT>M</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, M)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>an element <TT>E</TT> of the <TT>Options</TT> list is
<TT>mirror(M)</TT> and <TT>M</TT> iis an input stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(output, stream, M)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>an element <TT>E</TT> of the <TT>Options</TT> list is
<TT>reposition(true)</TT> and it is not possible to reposition this stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(open, source_sink, reposition(true))</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicates. The <TT>mirror/1</TT> and <TT>buffering/1</TT> stream options
are GNU Prolog extensions.<BR>
<BR>
<A NAME="toc80"></A>
<H4 CLASS="subsubsection"><A NAME="htoc112">7.10.7</A>&nbsp;&nbsp;<TT>close/2</TT>,
 <TT>close/1</TT></H4>
<A NAME="close/2"></A>
 
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
close(+stream_or_alias, +close_option_list)<BR>
close(+stream_or_alias)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>close(SorA, Options)</TT> closes the stream associated with the stream-term
or alias <TT>SorA</TT>. If <TT>SorA</TT> is the standard input stream or the
standard output stream <TT>close/2</TT> simply succeeds else the associated
source/sink is physically closed. If <TT>SorA</TT> is the current input
stream the current input stream becomes the standard input stream
<TT>user_input</TT>. If <TT>SorA</TT> is the current output stream the
current output stream becomes the standard output stream
<TT>user_output</TT>.<BR>
<BR>
<B>Close options</B>: <TT>Options</TT> is a list of close options. For the
moment only one option is available:
<UL CLASS="itemize"><LI CLASS="li-itemize"><TT>force(true</TT>/<TT>false)</TT>: with <TT>false</TT>, if
an error occurs when trying to close the source/sink, the stream is not
closed and an error (<TT>system_error</TT> or <TT>resource_error</TT>) is
raised (but <TT>close/2</TT> succeeds). With <TT>true</TT>, if an error
occurs it is ignored and the stream is closed. The purpose of
<TT>force/1</TT> option is to allow an error handling routine to do its best
to reclaim resources. The default value is <TT>false</TT>.</UL>
<TT>close(SorA)</TT> is equivalent to <TT>close(SorA, [])</TT>.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Options</TT> is a partial list or a list with an element
<TT>E</TT> which is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Options</TT> is neither a partial list nor a list</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(list, Options)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>an element <TT>E</TT> of the <TT>Options</TT> list is neither a
variable nor a close-option</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(close_option, E)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> needs a special close (section&nbsp;<A HREF="gprolog034.html#Constant-term-streams">7.11</A>)</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>system_error(needs_special_close)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicates. The <TT>system_error(needs_special_close)</TT> is a
GNU Prolog extension.<BR>
<BR>
<A NAME="toc81"></A>
<H4 CLASS="subsubsection"><A NAME="htoc113">7.10.8</A>&nbsp;&nbsp;<TT>flush_output/1</TT>,
 <TT>flush_output/0</TT></H4>
<A NAME="flush-output/1"></A>
 
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
flush_output(+stream_or_alias)<BR>
flush_output</TT></DL>
<B>Description</B><BR>
<BR>
<TT>flush_output(SorA)</TT> sends any buffered output characters/bytes to
the stream.<BR>
<BR>
<TT>flush_output/0</TT> applies to the current output stream.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is an input stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(output, stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicates.<BR>
<BR>
<A NAME="toc82"></A>
<H4 CLASS="subsubsection"><A NAME="htoc114">7.10.9</A>&nbsp;&nbsp;<TT>current_stream/1</TT></H4>
<A NAME="current-stream/1"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
current_stream(?stream)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>current_stream(Stream)</TT> succeeds if there exists
a stream-term that unifies with <TT>Stream</TT>. This predicate is
re-executable on backtracking.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Stream</TT> is neither a variable nor a stream-term</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream, Stream)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc83"></A>
<H4 CLASS="subsubsection"><A NAME="htoc115">7.10.10</A>&nbsp;&nbsp;<TT>stream_property/2</TT></H4>
<A NAME="stream-property/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
stream_property(?stream, ?stream_property)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>stream_property(Stream, Property)</TT> succeeds if
<TT>current_stream(Stream)</TT> succeeds (section&nbsp;<A HREF="#current-stream/1">7.10.9</A>) and if
<TT>Property</TT> unifies with one of the properties of the stream. This
predicate is re-executable on backtracking.<BR>
<BR>
<B>Stream properties</B>:
<UL CLASS="itemize"><LI CLASS="li-itemize"><TT>file_name(F)</TT>: the name of the connected 
source/sink.<BR>
<BR>
<LI CLASS="li-itemize"><TT>mode(M)</TT>: <TT>M</TT> is the open mode (<TT>read</TT>,
<TT>write</TT>, <TT>append</TT>).<BR>
<BR>
<LI CLASS="li-itemize"><TT>input</TT>: if it is an input stream.<BR>
<BR>
<LI CLASS="li-itemize"><TT>output</TT>: if it is an output stream.<BR>
<BR>
<LI CLASS="li-itemize"><TT>alias(A)</TT>: <TT>A</TT> is an alias of the stream.<BR>
<BR>
<LI CLASS="li-itemize"><TT>mirror(M)</TT>: <TT>M</TT> is a mirror stream of the 
stream.<BR>
<BR>
<LI CLASS="li-itemize"><TT>type(T)</TT>: <TT>T</TT> is the type of the stream
(<TT>text</TT>, <TT>binary</TT>).<BR>
<BR>
<LI CLASS="li-itemize"><TT>reposition(R)</TT>: <TT>R</TT> is the reposition
boolean (<TT>true</TT>, <TT>false</TT>).<BR>
<BR>
<LI CLASS="li-itemize"><TT>eof_action(A)</TT>: <TT>A</TT> is the end-of-file
action (<TT>error</TT>, <TT>eof_code</TT>, <TT>reset</TT>).<BR>
<BR>
<LI CLASS="li-itemize"><TT>buffering(B)</TT>: <TT>B</TT> is the buffering mode
(<TT>none</TT>, <TT>line</TT>, <TT>block</TT>).<BR>
<BR>
<LI CLASS="li-itemize"><TT>end_of_stream(E)</TT>: <TT>E</TT> is the
current end-of-stream status (<TT>not</TT>, <TT>at</TT>, <TT>past</TT>). If
the stream position is end-of-stream then <TT>E</TT> is unified with
<TT>at</TT> else if the stream position is past-end-of-stream then <TT>E</TT>
is unified with <TT>past</TT> else <TT>E</TT> is unified with <TT>not</TT>.<BR>
<BR>
<LI CLASS="li-itemize"><TT>position(P)</TT>: <TT>P</TT> is the stream-position
term associated with the current position.</UL>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Stream</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Stream</TT> is neither a variable nor a stream-term</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream, Stream)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Property</TT> is neither a variable nor a stream property</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_property, Property)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Property</TT> = <TT>file_name(E)</TT>,<TT> mode(E)</TT>,
<TT>alias(E)</TT>, <TT>end_of_stream(E)</TT>, <TT>eof_action(E)</TT>,
<TT>reposition(E)</TT>, <TT>type(E)</TT> or <TT>buffering(E)</TT> and
<TT>E</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, E)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicate. The <TT>buffering/1</TT> property is a GNU Prolog extension.<BR>
<BR>
<A NAME="toc84"></A>
<H4 CLASS="subsubsection"><A NAME="htoc116">7.10.11</A>&nbsp;&nbsp;<TT>at_end_of_stream/1</TT>,
 <TT>at_end_of_stream/0</TT></H4>
 
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
at_end_of_stream(+stream_or_alias)<BR>
at_end_of_stream</TT></DL>
<B>Description</B><BR>
<BR>
<TT>at_end_of_stream(SorA)</TT> succeeds if the stream associated with
stream-term or alias <TT>SorA</TT> has a stream position end-of-stream or
past-end-of-stream. This predicate can be defined using
<TT>stream_property/2</TT> (section&nbsp;<A HREF="#stream-property/2">7.10.10</A>).<BR>
<BR>
<TT>at_end_of_stream/0</TT> applies to the current input stream.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is an output stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(input, stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicates. The <TT>permission_error(input, stream, SorA)</TT> is a
GNU Prolog extension.<BR>
<BR>
<A NAME="toc85"></A>
<H4 CLASS="subsubsection"><A NAME="htoc117">7.10.12</A>&nbsp;&nbsp;<TT>stream_position/2</TT></H4>
<A NAME="stream-position/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
stream_position(+stream_or_alias, ?stream_position)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>stream_position(SorA, Position)</TT> succeeds unifying
<TT>Position</TT> with the stream-position term associated with the current
position of the stream-term or alias <TT>SorA</TT>. This predicate can be
defined using <TT>stream_property/2</TT> (section&nbsp;<A HREF="#stream-property/2">7.10.10</A>).<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Position</TT> is neither a variable nor a stream-position term</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_position, Position)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc86"></A>
<H4 CLASS="subsubsection"><A NAME="htoc118">7.10.13</A>&nbsp;&nbsp;<TT>set_stream_position/2</TT></H4>
<A NAME="set-stream-position/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
set_stream_position(+stream_or_alias, +stream_position)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>set_stream_position(SorA, Position)</TT> sets the position of
the stream associated with the stream-term or alias <TT>SorA</TT> to
<TT>Position</TT>. <TT>Position</TT> should have previously been returned by
<TT>stream_property/2</TT> (section&nbsp;<A HREF="#stream-property/2">7.10.10</A>) or by
<TT>stream_position/2</TT> (section&nbsp;<A HREF="#stream-position/2">7.10.12</A>).<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Position</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Position</TT> is neither a variable nor a stream-position term</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_position, Position)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> has stream property <TT>reposition(false)</TT></TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(reposition, stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
ISO predicate.<BR>
<BR>
<A NAME="toc87"></A>
<H4 CLASS="subsubsection"><A NAME="htoc119">7.10.14</A>&nbsp;&nbsp;<TT>seek/4</TT></H4>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
seek(+stream_or_alias, +stream_seek_method, +integer, ?integer)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>seek(SorA, Whence, Offset, NewOffset)</TT> sets the position of
the stream associated with the stream-term or alias <TT>SorA</TT> to
<TT>Offset</TT> according to <TT>Whence</TT> and unifies <TT>NewOffset</TT>
with the new offset from the beginning of the file. <TT>seek/4</TT> can only
be used on binary streams. <TT>Whence</TT> is an atom from:
<UL CLASS="itemize"><LI CLASS="li-itemize"><TT>bof</TT>: the position is set relatively to the begin of the file
(<TT>Offset</TT> should be &#8805; 0).<BR>
<BR>
<LI CLASS="li-itemize"><TT>current</TT>: the position is set relatively to the current
position (<TT>Offset</TT> can be &#8805; 0 or &#8804; 0).<BR>
<BR>
<LI CLASS="li-itemize"><TT>eof</TT>: the position is set relatively to the end of the file
(<TT>Offset</TT> should be &#8804; 0).</UL>
This predicate is an interface to the C Unix function <TT>lseek(2)</TT>.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Whence</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Offset</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Whence</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, Whence)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Whence</TT> is an atom but not a valid stream seek method</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_seek_method, Whence)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Offset</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Offset)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>NewOffset</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, NewOffset)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> has stream property <TT>reposition(false)</TT></TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(reposition, stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is associated with a text stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(reposition, text_stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc88"></A>
<H4 CLASS="subsubsection"><A NAME="htoc120">7.10.15</A>&nbsp;&nbsp;<TT>character_count/2</TT></H4>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
character_count(+stream_or_alias, ?integer)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>character_count(SorA, Count)</TT> unifies <TT>Count</TT> with the
number of characters/bytes read/written on the stream associated with
stream-term or alias <TT>SorA</TT>.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Count</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Count)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc89"></A>
<H4 CLASS="subsubsection"><A NAME="htoc121">7.10.16</A>&nbsp;&nbsp;<TT>line_count/2</TT></H4>
<A NAME="line-count/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
line_count(+stream_or_alias, ?integer)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>line_count(SorA, Count)</TT> unifies <TT>Count</TT> with the number of
lines read/written on the stream associated with the stream-term or alias
<TT>SorA</TT>. This predicate can only be used on text streams.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Count</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Count)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is associated with a binary stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(access, binary_stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc90"></A>
<H4 CLASS="subsubsection"><A NAME="htoc122">7.10.17</A>&nbsp;&nbsp;<TT>line_position/2</TT></H4>
<A NAME="line-position/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
line_position(+stream_or_alias, ?integer)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>line_position(SorA, Count)</TT> unifies
<TT>Count</TT> with the number of characters read/written on the current
line of the stream associated with the stream-term or alias
<TT>SorA</TT>. This predicate can only be used on text streams.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Count</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Count)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is associated with a binary stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(access, binary_stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc91"></A>
<H4 CLASS="subsubsection"><A NAME="htoc123">7.10.18</A>&nbsp;&nbsp;<TT>stream_line_column/3</TT></H4>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
stream_line_column(+stream_or_alias, ?integer, ?integer)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>stream_line_column(SorA, Line, Column)</TT> unifies <TT>Line</TT>
(resp. <TT>Column</TT>) with the current line number (resp. column number)
of the stream associated with the stream-term or alias <TT>SorA</TT>. This
predicate can only be used on text streams. Note that <TT>Line</TT>
corresponds to the value returned by <TT>line_count/2</TT> + 1
(section&nbsp;<A HREF="#line-count/2">7.10.16</A>) and <TT>Column</TT> to the value returned
by <TT>line_position/2</TT> + 1 (section&nbsp;<A HREF="#line-position/2">7.10.17</A>).<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Line</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Line)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Column</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Column)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is associated with a binary stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(access, binary_stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc92"></A>
<H4 CLASS="subsubsection"><A NAME="htoc124">7.10.19</A>&nbsp;&nbsp;<TT>set_stream_line_column/3</TT></H4>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
set_stream_line_column(+stream_or_alias, +integer, +integer)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>set_stream_line_column(SorA, Line, Column)</TT> sets the stream
position of the stream associated with the stream-term or alias <TT>SorA</TT>
according to the line number <TT>Line</TT> and the column number
<TT>Column</TT>. This predicate can only be used on text streams. It first
repositions the stream to the beginning of the file and then reads character
by character until the required position is reached.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Line</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Column</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Line</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Line)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Column</TT> is neither a variable nor an integer</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(integer, Column)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is associated with a binary stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(reposition, binary_stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> has stream property <TT>reposition(false)</TT></TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(reposition, stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc93"></A>
<H4 CLASS="subsubsection"><A NAME="htoc125">7.10.20</A>&nbsp;&nbsp;<TT>add_stream_alias/2</TT></H4>
<A NAME="add-stream-alias/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
add_stream_alias(+stream_or_alias, +atom)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>add_stream_alias(SorA, Alias)</TT> adds <TT>Alias</TT> as a new alias
to the stream associated with the stream-term or alias <TT>SorA</TT>.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Alias</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Alias</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, Alias)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Alias</TT> is already associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(add_alias, source_sink, alias(Alias))</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc94"></A>
<H4 CLASS="subsubsection"><A NAME="htoc126">7.10.21</A>&nbsp;&nbsp;<TT>current_alias/2</TT></H4>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
current_alias(?stream, ?atom)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>current_alias(Stream, Alias)</TT> succeeds if
<TT>current_stream(Stream)</TT> succeeds (section&nbsp;<A HREF="#current-stream/1">7.10.9</A>) and if
<TT>Alias</TT> unifies with one of the aliases of the stream. It can be
defined using <TT>stream_property/2</TT> (section&nbsp;<A HREF="#stream-property/2">7.10.10</A>). This
predicate is re-executable on backtracking.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Stream</TT> is neither a variable nor a stream-term</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream, Stream)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Alias</TT> is neither a variable nor an atom</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>type_error(atom, Alias)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc95"></A>
<H4 CLASS="subsubsection"><A NAME="htoc127">7.10.22</A>&nbsp;&nbsp;<TT>add_stream_mirror/2</TT></H4>
<A NAME="add-stream-mirror/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
add_stream_mirror(+stream_or_alias, +stream_or_alias)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>add_stream_mirror(SorA, Mirror)</TT> adds the stream associated with
the stream-term or alias <TT>Mirror</TT> as a new mirror to the stream
associated with the stream-term or alias <TT>SorA</TT>. After this, all
characters (or bytes) read from (or written to) <TT>SorA</TT> are also
written to <TT>Mirror</TT>. This mirroring occurs until <TT>Mirror</TT> is
explicitely removed using <TT>remove_stream_mirror/2</TT>
(section&nbsp;<A HREF="#remove-stream-mirror/2">7.10.23</A>) or implicitely when <TT>Mirror</TT> is closed.
Several mirror streams can be associated with a same stream. If <TT>Mirror</TT>
represents the same stream as <TT>SorA</TT> or if <TT>Mirror</TT> is already
a mirror for <TT>SorA</TT>, no mirror is added.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mirror</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mirror</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, Mirror)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mirror</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, Mirror)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mirror</TT> is an input stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(output, stream, Mirror)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc96"></A>
<H4 CLASS="subsubsection"><A NAME="htoc128">7.10.23</A>&nbsp;&nbsp;<TT>remove_stream_mirror/2</TT></H4>
<A NAME="remove-stream-mirror/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
remove_stream_mirror(+stream_or_alias, +stream_or_alias)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>remove_stream_mirror(SorA, Mirror)</TT> removes the stream associated
with the stream-term or alias <TT>Mirror</TT> from the list of mirrors of the
stream associated with the stream-term or alias <TT>SorA</TT>. This predicate
fails if <TT>Mirror</TT> is not a mirror stream for <TT>SorA</TT>.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mirror</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mirror</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, Mirror)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Mirror</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, Mirror)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc97"></A>
<H4 CLASS="subsubsection"><A NAME="htoc129">7.10.24</A>&nbsp;&nbsp;<TT>current_mirror/2</TT></H4>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
current_mirror(?stream, ?stream)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>current_mirror(Stream, M)</TT> succeeds if
<TT>current_stream(Stream)</TT> succeeds (section&nbsp;<A HREF="#current-stream/1">7.10.9</A>) and if
<TT>M</TT> unifies with one of the mirrors of the stream. It can be
defined using <TT>stream_property/2</TT> (section&nbsp;<A HREF="#stream-property/2">7.10.10</A>). This
predicate is re-executable on backtracking.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Stream</TT> is neither a variable nor a stream-term</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream, Stream)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>M</TT> is neither a variable nor a stream-term</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream, M)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc98"></A>
<H4 CLASS="subsubsection"><A NAME="htoc130">7.10.25</A>&nbsp;&nbsp;<TT>set_stream_type/2</TT></H4>
<A NAME="set-stream-type/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
set_stream_type(+stream_or_alias, +atom)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>set_stream_type(SorA, Type)</TT> updates the type associated with
stream-term or alias <TT>SorA</TT>. The value of <TT>Type</TT> is an atom in
<TT>text</TT> or <TT>binary</TT> as for <TT>open/4</TT> (section&nbsp;<A HREF="#open/4">7.10.6</A>).
The type of a stream can only be changed before any input/output operation
is executed.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Type</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Type</TT> is neither a variable nor a valid type</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_type, Type)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left>An I/O operation has already been executed on <TT>SorA</TT></TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(modify, stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc99"></A>
<H4 CLASS="subsubsection"><A NAME="htoc131">7.10.26</A>&nbsp;&nbsp;<TT>set_stream_eof_action/2</TT></H4>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
set_stream_eof_action(+stream_or_alias, +atom)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>set_stream_eof_action(SorA, Action)</TT>
updates the <TT>eof_action</TT> option associated with the stream-term or
alias <TT>SorA</TT>. The value of <TT>Action</TT> is one of the atoms
<TT>error</TT>, <TT>eof_code</TT>, <TT>reset</TT> as for <TT>open/4</TT> (section&nbsp;<A HREF="#open/4">7.10.6</A>).<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Action</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Action</TT> is neither a variable nor a valid eof action</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(eof_action, Action)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is an output stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>permission_error(modify, stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>
<A NAME="toc100"></A>
<H4 CLASS="subsubsection"><A NAME="htoc132">7.10.27</A>&nbsp;&nbsp;<TT>set_stream_buffering/2</TT></H4>
<A NAME="set-stream-buffering/2"></A>
 
<B>Templates</B>
<DL CLASS="list" COMPACT="compact"><DT CLASS="dt-list"><DD CLASS="dd-list"><TT>
set_stream_buffering(+stream_or_alias, +atom)</TT></DL>
<B>Description</B><BR>
<BR>
<TT>set_stream_buffering(SorA, Buffering)</TT>
updates the buffering mode associated with the stream-term or alias
<TT>SorA</TT>. The value of <TT>Buffering</TT> is one of the atoms
<TT>none</TT>, <TT>line</TT> or <TT>block</TT> as for <TT>open/4</TT>
(section&nbsp;<A HREF="#open/4">7.10.6</A>). This predicate may only be used after opening a stream
and before any other operations have been performed on it.<BR>
<BR>
<B>Errors</B><BR>
<TABLE CELLSPACING=2 CELLPADDING=0>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Buffering</TT> is a variable</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>instantiation_error</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>Buffering</TT> is neither a variable nor a valid buffering
mode</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(buffering_mode, Buffering)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is neither a variable nor a stream-term or alias</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>domain_error(stream_or_alias, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR>
<TR><TD VALIGN=top ALIGN=left><TT>SorA</TT> is not associated with an open stream</TD>
<TD VALIGN=top ALIGN=center NOWRAP>&nbsp;&nbsp;</TD>
<TD VALIGN=top ALIGN=left><TT>existence_error(stream, SorA)</TT></TD>
</TR>
<TR><TD BGCOLOR=black COLSPAN=3><TABLE BORDER=0 WIDTH="100%" CELLSPACING=0 CELLPADDING=1><TR><TD></TD></TR></TABLE></TD>
</TR></TABLE><BR>
<B>Portability</B><BR>
<BR>
GNU Prolog predicate.<BR>
<BR>

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