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<TITLE>3.6 Comments</TITLE>
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<P><FONT SIZE="5">3.6 Comments</FONT><BR>
<P>When FunnelWeb encounters the <SAMP>@!</SAMP>
sequence during its left-to-right scan of the line, it
throws away the rest of the line (including the EOL) without
analysing it further. Comments can appear in any line except
"<TT>@i</TT>", "<TT>@t</TT>", and "<TT>@p</TT>" lines.
<P>FunnelWeb comments can be used to insert comments into
your input file that will neither appear in the product
files nor in the documentation file, but will be solely for
the benefit of those reading and editing the input file
directly. Example:
<P><PRE>
@! I have used a quick macro for this definition
@! as it will be used often.
@$@#C@{--@}
</PRE>
<P>Because comments are defined to include the end-of-line
marker, care must be taken when they are being added or
removed within the text of macro bodies. For example the
text fragment
<P>
<PRE>
for (i=0;i<MAXVAL;i++) @! Print out a[0..MAXVAL-1].
printf("%u\n",a[i]);
</PRE>
<P>will expand to
<P>
<PRE>
for (i=0;i<MAXVAL;i++) printf("%u\n",a[i]);
</PRE>
<P>This problem really has no solution; if FunnelWeb
comments were defined to omit the end of line marker, the
expanded text would contain trailing blanks! As it is,
FunnelWeb comments are designed to support single line
comments which can be inserted and removed as a line without
causing trouble. For example:
<P>
<PRE>
@! Print out a[0..MAXVAL-1].
for (i=0;i<MAXVAL;i++)
printf("%u\n",a[i]);
</PRE>
<P>If you want a comment construct that does not enclose
the end of line marker, combine the insert end of line
construct <SAMP>@+</SAMP> with the comment construct
<SAMP>@!</SAMP> as in
<P>
<PRE>
for (i=0;i<MAXVAL;i++) @+@! Print out a[0..MAXVAL-1].
printf("%u\n",a[i]);
</PRE>
<P>FunnelWeb comments should really only be used to
comment the FunnelWeb constructs being used in the input
file. Comments on the target code are best placed in
comments in the target language or in the documenting text
surrounding the macro definitions. In the example above, a C
comment would have been more appropriate.
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