Doing upgrades and want to split the current composite grammar to serve as a
base for two new grammars that will share approx 90% rules. After going through
the process of splitting out tokens from rules, I'm left with:
parser RootParser;
value_expr:
..
;
...
lexer RootLexer;
LeftParen: '(';
...
grammar Timer;
options{
tokenVocab = RootLexer;
}
import RootParser
@header{package com.timer.parser;}
start: value_expr;
...
grammar Calculator;
options{
tokenVocab = RootLexer;
}
import RootParser
@header{package com.timer.parser;}
start: value_expr | control | txt_alias;
control_spec:
...
Although the grammar in the above checks out, the problem surfaces when
generating source code - specifically the token files. Unlike with composite
grammar where the lexer (RootLexer.java) is generated when generating the
parser, I manually generate the lexer and subsequently generate the parser. The
generated files are: RootLexer.java, RootLexer.tokens, TimerParser.java,
Timer_RootParser.java, Timer.tokens, CalculatorParser.java,
Calculator_RootParser.java, Calculator.tokens.
On inspecting the token files, I noticed the token values in the lexer file did
not match up with the equivalents in the two parser token files. From what I
understand in all that I read, this cannot be as it will cause incorrect switch
jumps, amongst other errors.
As alternatives, I tried:
- remove the tokenVocab options and import both RootParser and RootLexer
- import the RootLexer into RootParser instead. This generates an error "parser
rule value_expr not allowed in lexer" which seems to have something to do with
the "parser grammar RootParser" definition on the opening line
- removed "parser" qualifier from grammar definition. Generated error due to
importing combined grammar Timer/Calculator.
- tried import instead of tokenVocab on RootLexer. It too generated combined
grammar error.
Is there some way to specify the created lexer when generating the parser?
I dislike the idea of having to resort to two grammars that are essentially the
same. Any help would be much appreciated.
Roger
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