parsing - Ignoring whitespace on a per-parser-rule basis in Antlr4 -


my grammar must ignore whitespaces part, except in contexts. answers this question advises define specific lexer rules handle exceptions want.

the problem (i think) cannot handle such cases @ lexer level, since seem triggered high @ parser level.

to more specific: want recognize like

myrule:    myparsetree1 operator myparsetree2 // ws skipped    | myparsetree1 ws sensitiveoperator ws myparse // ws carries meaning

keeping in mind have ws -> skip rule because in of grammar whitespaces should skipped.

in xtext, rules can specify on rule-scoped basis hidden tokens apply within rule's scope:

myrule (hidden comments):   ... // ws reaches parser, comments don't  myrule2 (hidden ws, comments):   ... // ws skipped, comments

but clueless antlr4.

if want skip tokens depending on grammar context should have @ question here given procedure described skipping whitespace (as want it).


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