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

[Steve Litt]

Thanks Chris,

Changing "." to either ".*", ".+", "[^\n]*" or "[^\n]+" all solve the
problem with multiple printables on one line, but still throw a syntax
error when two lines follow each other without an intervening
blankline. In other words, it calls a paragraph of more than one line
a syntax error.

I've already split paratext into multiple LINE tokens which represent a
line without its NL, and now I'm thinking of splitting line into
multiple chars ("[^\n]"). Perhaps this will make the rules less
complicated, though longer.

Thanks,

SteveT

Steve Litt 

Autumn 2023 featured book: Rapid Learning for the 21st Century
http://www.troubleshooters.com/rl21
 


Chris verBurg said on Tue, 12 Dec 2023 18:57:08 -0800

>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
>>
>>