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  1. %{
  2. #include <ctype.h>
  3. #include <stdio.h>
  4. #define YYSTYPE double
  5. int yylex(void);
  6. void yyerror(const char *s) { fprintf(stderr, "error: %s\n", s); }
  7. %}
  8.  
  9. %token NUMBER
  10. %left '+' '-'
  11. %left '*' '/'
  12. %right UMINUS
  13.  
  14. %%
  15. lines : lines expr '\n' { printf("%g\n", $2); }
  16.       | lines '\n'
  17.       | /* empty */
  18.       ;
  19. expr : expr '+' expr { $$ = $1 + $3; }
  20.      | expr '-' expr { $$ = $1 - $3; }
  21.      | expr '*' expr { $$ = $1 * $3; }
  22.      | expr '/' expr { $$ = $1 / $3; }
  23.      | '-' expr %prec UMINUS { $$ = -$2; }
  24.      | '(' expr ')' { $$ = $2; }
  25.      | NUMBER
  26.      ;
  27. %%
  28.  
  29. int yylex(void)
  30. {
  31.     int c;
  32.     /* skip spaces and tabs */
  33.     while ((c = getchar()) == ' ' || c == '\t')
  34.         ;
  35.     if (c == EOF) return 0;
  36.     if (c == '.' || isdigit(c)) {
  37.         ungetc(c, stdin);
  38.         if (scanf("%lf", &yylval) != 1) return 0;
  39.         return NUMBER;
  40.     }
  41.     return c; /* return character as token (e.g., '+', '\n', etc.) */
  42. }
  43.  
Success #stdin #stdout #stderr 0.03s 6908KB
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Standard input is empty
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Standard output is empty
stderr
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ERROR: /home/r7CPSf/prog:42:1: Syntax error: end_of_file_in_quasi_quotation
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/eCsIGw
language:
Prolog (swi 7.6.4)
created:
14 hours ago
visibility:
public

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