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# In a grammar, how do I reuse a proto'ed definition? Here for | |
# example, I want <ld> to use some <elem>: | |
#use Grammar::Debugger; | |
grammar Foo { | |
proto token elem {*} | |
token elem:sym<let> { <[a..z]> } | |
token elem:sym<dig> { <[0..9]> } | |
token anys { <elem>+ } | |
# A <let> followed by a <dig>. None of these work. Some fail | |
# to match, some fail to compile. | |
# token ld { <let> <dig> } | |
# token ld { sym<let> sym<dig> } | |
# token ld { elem:sym<let> elem:sym<dig> } | |
# token ld { elem<let> elem<dig> } | |
token TOP { <anys> | \( <ld> \) } | |
}; | |
# Matches <TOP> with <anys>. | |
#say Foo.parse('bar42'); | |
# Can't get this to match <TOP> with parenthesized <ld>. | |
say Foo.parse('(k9)'); | |
=finish | |
- -------------------------------------------------------------------- | |
Two solutions were suggested by ShimmerFairy#raku@freenode.net.irc | |
1. Factor out the names of the required tokens: | |
token let { <[a..z]> } | |
token dig { <[0..9]> } | |
token elem:sym<let> { <let> } | |
token elem:sym<dig> { <dig> } | |
token ld { <let> <dig> } | |
2. Define <ld> like this: | |
token ld { <elem:sym<let>> <elem:sym<dig>> } | |
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Hm, great. The sym thing is something I've avoided as hard to understand, but I'm at a point in my own project I need to buckle down and study it more closely. @ShimmerFairy has a lot of Raku experience and it would be nice if she could add more to our docs about the solution and more.