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<TITLE>3.5 Inserting Arbitrary Characters into the Text</TITLE>
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<P><FONT SIZE="5">3.5 Inserting Arbitrary Characters into the Text</FONT><BR>
<P>While FunnelWeb does not tolerate unprintable
characters in the input file (except for the end of line
character), it does allow the user to specify that
unprintable characters appear in the product file. The
<SAMP>@^</SAMP> sequence inserts a single
character of the user's choosing into the text. The
character can be specified by giving its ASCII number in one
of four bases: binary, octal, decimal, and hexadecimal. Here
is the syntax:
<P>
<PRE>
control_sequence = "@^" char_spec
char_spec = binary | octal |
decimal | hexadecimal
binary = ("b" | "B")
"(" {binary_digit}8 ")"
octal = ("o" | "O" | "q" | "Q")
"(" {octal_digit}3 ")"
decimal = ("d" | "D")
"(" {decimal_digit}3 ")"
hexadecimal = ("h" | "H" | "x" | "X")
"(" {hex_digit}2 ")"
binary_digit = "0" | "1"
octal_digit = binary_digit | "2" | "3" |
"4" | "5" | "6" | "7"
decimal_digit = octal_digit | "8" | "9"
hex_digit = decimal_digit |
"A" | "B" | "C" | "D" | "E" | "F" |
"a" | "b" | "c" | "d" | "e" | "f"
</PRE>
<P>Example:
<PRE>
@! Unix Make requires that productions
@! commence with tab characters.
@^D(009)prog.o <- prog.c
</PRE>
<P>Note that the decimal "<TT>9</TT>" is expressed with
leading zeros as "<TT>009</TT>". FunnelWeb requires a fixed
number of digits for each base. Eight digits for base two,
three digits for base ten, three digits for base eight and
two digits for base sixteen.
<P>FunnelWeb treats the character resulting from a
<SAMP>@^</SAMP> sequence as ordinary text in every
sense. If your input file contains many instances of a
particular control character, you can package it up in a
macro like any other text. In particular, quick names can be
used to great effect:
<P>
<PRE>
@! Unix "Make" requires that productions
@! commence with tab characters.
@! So we define a macro with a quick name
@! as a tab character.
$@#T@{@^D(009)@}
@! And use it in our productions.
@#Tprog.o <- prog.c
@#Ta.out <- prog.o
</PRE>
<P>Warning: If you insert a Unix
newline character (decimal 10) into the text, FunnelWeb will
treat this as an end of line sequence regardless of what the
character sequence for end of line is on the machine upon
which it is running. Unix EOL is FunnelWeb's internal
representation for end of line. Thus, in the current version
of FunnelWeb, inserting character 10 into the text is
impossible unless this also happens to be the character used
by the operating system to mark the end of line.
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