On Wednesday, December 25, Alt Mcarter wrote:
> But I'm wondering, is there a way to write token var in such a way that it
> matches <[a..z]>+ EXCEPT when it is a keyword (print, for, to, next, etc.)?
You could use a negative code assertion --
#!/usr/bin/env raku
my @keywords = <print for to next>;
grammar G {
rule TOP {
<var>
}
rule var {
<id>
<!{ $<id> eq @keywords.any }>
}
token id {
<[a..z]>+
}
}
use Test;
ok G.parse('fine');
ok G.parse('finetoo');
nok G.parse('print');
nok G.parse('for');
nok G.parse('to');
nok G.parse('next');
ok G.parse('forth');
(you can also use before/after assertions --
see
<https://stackoverflow.com/questions/42538548/perl6-negating-multiple-words-and-permutations-of-their-chars-inside-a-regex>)
Brian
