RK == Rob Kinyon [EMAIL PROTECTED] writes:
Text-substitution macros would have to be handled in an earlier pass,
I still don't see evidence for this. Or maybe I do, but I don't see
any reason that the preprocessing pass must finish before the parsing
begins.
RK Mixing C and Perl ...
RK my $foo;
RK BEGIN { $foo = '}'; }
RK #define OPEN {
RK #define CLOSE $foo
RK void main (void)
RK OPEN
RK BEGIN { $foo = '{''; }
RK printf( I don't work\n );
RK CLOSE
RK How does that work out? The issue is that you can interrupt the
RK parsing process with executable code that can affect the parsing.
RK That's a good thing. It doesn't work so well with text-substitution,
RK though. Hence, I would argue it should be disallowed.
from S06:
Macros (keyword: macro) are routines whose calls execute as soon
as they are parsed (i.e. at compile-time). Macros may return
another source code string or a parse-tree.
i see uses for text macros. sure they can trip you up but that is going
to be true about AST macros as well. macros are inherently trickier than
plain coding as you are dealing with another level at the same time. so
the author of your bad example should learn how to do that correctly and
not expect perfect DWIMMERY with an advanced technology.
and that excerpt also means that p6 macros are not done in a
preprocessing pass but at normal compile time as soon as the macro call
is fully parsed. so a text returning macro would run and the compiler
will replace the text of the parsed macro call and start reparsing with
the returned text. there may be some juggling of the main parse tree to
deal with this but it can be done without going too insane. :)
uri
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Uri Guttman -- [EMAIL PROTECTED] http://www.stemsystems.com
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