CODEWITHSUNDEEP
antlrlexer
Philip Loger
Philip Loger

Reputation: 1023

How I do... ? with lexer only rules on ANTLR

I’m trying to implement a simple parsing over custom .c files with added syntax.

Ex: test.c .

// I don’t need this in output
int func1(int a, int b);

//I need this.
@parseme int func2(int a, int b);

//and this …
@parseme
void func3() 
{
Int a;
//put here where ever 
…
{
                                //inside block
                }
return;
}

.

I want to use a fuzzy parsing approach on the lexer phase then, on the parser rules, rewrite token with TokenRewriteStream and templates.

Well it’s a lexer piece … 

lexer grammar Lexi;

options {filter = true;}

// Pick everything between @parseme and ';' or '{ }'
METHOD
                :               HEADER .* (';' | BODY )
                ;

fragment
HEADER
                :               '@' ('parseme' | 'PARSEME') ;

fragment
BODY:   '{' .* '}' ;

.

… The problem is simple for a expert look: 1- Lexer stop parse when found ‘;’ before to reach the last ‘}’ on “ @parseme void func3() …. “ 2- Lexer stop parse when found inside block right curly. 3- And surely more cases don’t tested yet.

The problem is really obvious. Is the solution too?? I hope soo !! 

Thanks.

Upvotes: 0

Views: 186

Answers (1)

Philip Loger
Philip Loger

Reputation: 1023

Answer my self.

lexer grammar Lexi;

options {filter = true;}


// Pick everything between @parseme and ';' or '{}'
METHOD
    :   METHOD_HEADER (~'{')* METHOD_END ;

fragment
METHOD_HEADER
    :   '@' ('parseme' | 'PARSEME') ;

fragment
METHOD_END
    :   (';' | BLOCK ) ;

fragment
BLOCK
    :   '{' ( ~('{' | '}') | BLOCK )* '}' ;


WS  :   (' '|'\r'|'\t'|'\n')+ ;

The solution was very simple.

Upvotes: 1

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