Re: simple parsing problem

[Steve Fernandez]

anton wilson wrote:

>The following is a simple test grammer I wrote to recognize token 
sequences
>composed of an optional INDENT or DEDENT token followed by an ID and 
then a
>NEWLINE.
>
>When the lexer sends it the token sequence:
>
>ID
>NEWLINE
>INDENT
>ID
>NEWLINE
>DEDENT
>ID
>NEWLINE
>
>there is a syntax error called between the DEDENT and the ID.
>Is there something wrong with my grammer? Thanks.
>
>
>%token NEWLINE INDENT DEDENT ID
>
>
>%%
>
>lines:               {printf("lines\n");}
>| lines line         {printf("lines\n");}
>;
>line:  id newline        {printf("line\n");}
>| dedent  id newline        {printf("line\n");}
>| indent  id newline        {printf("line\n");}
>;
>newline: NEWLINE {printf("newline token\n");}
>;
>indent:  INDENT  {printf("indent token\n");}
>;
>dedent:  DEDENT {printf("dedent token\n");}
>;
>id: ID {printf("id token\n");}
>
>%%
>
>
>
>_______________________________________________
>address@hidden http://mail.gnu.org/mailman/listinfo/help-bison
>
>
>
Hi Anton,

        Is this the output you expected? Seems correct to me :-)

    address@hidden:~# lex test.l
    address@hidden:~# yacc -d test.y -o test.tab.c
    address@hidden:~# ./test < input
    lines
    id token

    newline token
    line
    lines

    indent token

    id token

    newline token
    line
    lines

    dedent token

    id token

    newline token
    line
    lines

        I think the error was caused because of the extra spaces that
were in your grammar between dedent and id. The source files that I used
are attached. Let me know if this was the problem

Regards,
Steve Fernandez.

--
Registered Linux User #211615
Registered Linux Machine #98619

"I am not young enough to know everything."



%{

        #include "lex.yy.c"
        
        int yylex ( void );
        int yyerror ( char * );
        int main ( void );
        
%}
        
%token NEWLINE INDENT DEDENT ID



%%

lines :                         { printf ( "lines\n" ); }
        |       lines line      { printf ( "lines\n" ); }
;

line :          id newline              {printf("line\n");}
        |       dedent id newline       {printf("line\n");}
        |       indent id newline       {printf("line\n");}
;

newline :       NEWLINE         { printf ( "newline token\n" ); }
;

indent  :       INDENT          { printf ( "indent token\n" ); }
;

dedent  :       DEDENT          { printf ( "dedent token\n" ); }
;

id      :       ID              { printf ( "id token\n" ); }
;

%%

int main ( void )
{

        yyparse ( );
        return ( 0 );
        
}

int yyerror ( char *error )
{

        printf ( "%s\n", error );
        return ( 0 );
        
}

%option noyywrap

%{

        #include "test.tab.h"
        
%}


%%


NEWLINE         return ( NEWLINE );
INDENT          return ( INDENT );
DEDENT          return ( DEDENT );
ID              return ( ID );

ID
NEWLINE
INDENT
ID
NEWLINE
DEDENT
ID
NEWLINE

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