Re: Syntax error if paragraph contains more than 1 printable character

[Chris verBurg]

Hey Steve,

My reading of your code is that PARATEXT will only ever be a single
character.  I'm thinking you want the flex rule to be ".*" (etc) instead of
just ".".

I'm curious whether your paragraphs are allowed to contain NLs.  If so,
you're going to have to include them in the PARATEXT token value, and also
update it to not match more than one.  I don't know offhand if there's some
cleverness with trailing context that could be used there.

-Chris


On Tue, Dec 12, 2023 at 9:29 AM Steve Litt <slitt@troubleshooters.com>
wrote:

> Hi all,
>
> I'm creating a parser that takes a text file whose paragraphs are
> separated by blank lines. Unfortunately, if the input file contains a
> paragraph with more than one non-space character, it gives me a syntax
> error via yyerror(). So the following works, where ===== etc are not in
> the inpyut file but just signify beginning and end of file:
>
> ================
> a
>
> b
>
> c
>
> ================
>
> The following throws a syntax error:
>
> ================
> a
>
> bx
>
> c
>
> ================
>
> The following also throws a syntax error:
>
> ================
> a
>
> b
> x
>
> c
>
> ================
>
> I'd appreciate any guidance as to what is wrong with my Flex and Bison
> programs (I suspect my rules in the rules section of Bison). My Flex
> and Bison programs follow, once again delineated by lines of equal
> signs that don't exist in the program:
>
> ======= Flex Program =========
> %option noinput nounput
> %{
> #include "paragraphs.tab.h"
> %}
>
> %%
>
> [ \t]*\n    {strcpy (yylval.y_char, yytext); return NL;  }
> .           {strcpy (yylval.y_char, yytext); return PARATEXT; }
>
> %%
>
>
> int yywrap(void)
> {
>      return 1;
> }
>
> int yyerror(char *errormsg)
> {
>       fprintf(stderr, "%s\n", errormsg);
>       exit(1);
> }
> ================
>
>
> ======= Bison Program =========
> %{
>
> #include <stdio.h>
> #include <stdlib.h>
> int yylex(void);
> int yyerror (char *errmsg);
> #define EOF_ 0
> %}
>
> %union {
>         char    y_char [10000];
> }
> %token <y_char>   PARATEXT
> %token <y_char>   NL
> %%
>
> wholefile : wholefile2 {printf("End of file.\n");};
>
> wholefile2 : toptrash {printf("Beginning of file.\n");}
>   multichunk {printf("dia multichunk\n");}
> ;
>
> toptrash : %empty {printf("dia empty multitrash\n");}
>   | toptrash {printf("dia another toptrash\n");}
>   NL {printf("dia another NL in toptrash\n");}
> ;
>
> multichunk : %empty {printf("dia empty multichunk\n");}
>   | multichunk chunk {printf("dia multichunk chunk\n");}
> ;
>
> chunk : PARATEXT { printf("%s %s\n", "PARATEXT", $1); }
>   parend {printf("dia parend\n");}
> ;
>
> parend :
>   multinewline {printf("dia multinewline\n");}
>   | YYEOF {printf("dia YYEOF\n");}
>
> multinewline : NL  { printf("%s%s", "NL_tok1",$1); }
>   NL   { printf("%s%s", "NL_tok2",$1); }
>   | multinewline NL   { printf("%s\n", "dia multinewline NL"); }
> ;
>
> %%
>
> int main(int argc, char *argv[]){
>         printf("\nStarting...\n");
>         printf("dia value of YYEOF is %d\n", YYEOF);
>         yyparse();
>         printf("\nFinished...\n");
> }
>
> ================
>
> Thanks,
>
> SteveT
>
> Steve Litt
>
> Autumn 2023 featured book: Rapid Learning for the 21st Century
> http://www.troubleshooters.com/rl21
>
>