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  1. %{
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4. #include <ctype.h>
  5. int yylex();
  6. void yyerror(const char *s);
  7. int yylval;
  8. %}
  9. %token NUMBER
  10. %left '+' '-'
  11. %left '*' '/'
  12. %right UMINUS
  13. %%
  14.  
  15. stmt_list: stmt_list expr '\n' { printf("Result: %d\n", $2); }
  16.          | expr '\n' { printf("Result: %d\n", $1); }
  17.          ;
  18.  
  19. expr: expr '+' expr { $$ = $1 + $3; }
  20.     | expr '-' expr { $$ = $1 - $3; }
  21.     | expr '*' expr { $$ = $1 * $3; }
  22.     | expr '/' expr {
  23.         if ($3 == 0) {
  24.             yyerror("Division by zero!");
  25.             $$ = 0;
  26.         } else {
  27.             $$ = $1 / $3;
  28.         }
  29.     }
  30.     | '-' expr %prec UMINUS { $$ = -$2; }
  31.     | '(' expr ')' { $$ = $2; }
  32.     | NUMBER { $$ = $1; }
  33.     ;
  34.  
  35. %%
  36.  
  37. int yylex() {
  38.     int c;
  39.  
  40.     while ((c = getchar()) == ' ' || c == '\t');
  41.     if (isdigit(c)) {
  42.         ungetc(c, stdin);
  43.         scanf("%d", &yylval);
  44.         return NUMBER;
  45.     }
  46.     if (c == '\n' || c == EOF) return c;
  47.     return c;
  48. }
  49.  
  50. void yyerror(const char *s) {
  51.     fprintf(stderr, "Error: %s\n", s);
  52. }
  53.  
  54.  
Success #stdin #stdout #stderr 0.03s 6952KB
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stdin
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Standard input is empty
stdout
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Standard output is empty
stderr
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ERROR: /home/N7ptDm/prog:53:0: Syntax error: end_of_file_in_quasi_quotation
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/mPAzf7
language:
Prolog (swi 7.6.4)
created:
11 days ago
visibility:
public

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