trcombine

trcombine

Summary

Combine a split Antlr4 grammar

Description

Combine two grammars into one. One grammar must be a lexer grammar, the other a parser grammar, order is irrelevant. The output is parse tree data.

Usage

trcombine  

Details

trcombine combines grammars that are known as "split grammars" (separate Antlr4 lexer and parser grammars) into one grammar, known as a "combined grammar". This refactoring is useful if a simplified grammar grammar is wanted, and if possible if the split grammar does not use the "superClass" option in one or the other grammars. The opposite refactoring is implemented by trsplit.

The split refactoring performs several operations:

• Combine the two files together, parser grammar first, then lexer grammar.
• Remove the grammarDecl for the lexer rules, and change the grammarDecl for the parser rules to be a combined grammar declaration. Rename the name of the parser grammar to not have "Parser" at the tail of the name.
• Remove the optionsSpec for the lexer section.
• Remove any occurrence of "tokenVocab" from the optionsSpec of the parser section.
• If the optionsSpec is empty, it is removed.

The order of the two grammars is ignored: the parser rules always will appear before the lexer rules.

Lexer modes will require manual fix-up.

Example

Consider the following grammar that is split.

Input to command

Lexer grammar in ExpressionLexer.g4:

lexer grammar ExpressionLexer;
VARIABLE : VALID_ID_START VALID_ID_CHAR* ;
fragment VALID_ID_START : ('a' .. 'z') | ('A' .. 'Z') | '_' ;
fragment VALID_ID_CHAR : VALID_ID_START | ('0' .. '9') ;
INT : ('0' .. '9')+ ;
MUL : '*' ;
DIV : '/' ;
ADD : '+' ;
SUB : '-' ;
LP : '(' ;
RP : ')' ;
WS : [ \r\n\t] + -> skip ;

Parser grammar in ExpressionParser.g4:

parser grammar ExpressionParser;
e : e ('*' | '/') e
 | e ('+' | '-') e
 | '(' e ')'
 | ('-' | '+')* a
 ;
a : number | variable ;
number : INT ;
variable : VARIABLE ;

Command

trcombine ExpressionLexer.g4 ExpressionParser.g4 | trprint > Expression.g4

Combined grammar in Expression.g4:

grammar Expression;
e : e ('*' | '/') e
 | e ('+' | '-') e
 | '(' e ')'
 | ('-' | '+')* a
 ;
a : number | variable ;
number : INT ;
variable : VARIABLE ;
VARIABLE : VALID_ID_START VALID_ID_CHAR* ;
fragment VALID_ID_START : ('a' .. 'z') | ('A' .. 'Z') | '_' ;
fragment VALID_ID_CHAR : VALID_ID_START | ('0' .. '9') ;
INT : ('0' .. '9')+ ;
MUL : '*' ;
DIV : '/' ;
ADD : '+' ;
SUB : '-' ;
LP : '(' ;
RP : ')' ;
WS : [ \r\n\t] + -> skip ;

The original grammars are left unchanged.

Current version

0.21.12 Removed Antlr 4.10 dependencies, clean up.