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  1. %option noyywrap
  2.  
  3. %{
  4. #include<stdio.h>
  5. #include<stdlib.h>
  6.  
  7. int num1 = 0, num2 = 0;
  8. char op;
  9. %}
  10.  
  11. %%
  12. [0-9]+    {
  13.               if(num1 == 0)
  14.                   num1 = atoi(yytext);
  15.               else
  16.                   num2 = atoi(yytext);
  17.           }
  18.  
  19. [\+\-\*/] {
  20.               op = yytext[0];
  21.           }
  22.  
  23. \n        {
  24.               switch(op)
  25.               {
  26.                   case '+':
  27.                       printf("Result = %d\n", num1 + num2);
  28.                       break;
  29.  
  30.                   case '-':
  31.                       printf("Result = %d\n", num1 - num2);
  32.                       break;
  33.  
  34.                   case '*':
  35.                       printf("Result = %d\n", num1 * num2);
  36.                       break;
  37.  
  38.                   case '/':
  39.                       if(num2 == 0)
  40.                           printf("Division by zero error\n");
  41.                       else
  42.                           printf("Result = %d\n", num1 / num2);
  43.                       break;
  44.  
  45.                   default:
  46.                       printf("Invalid operator\n");
  47.               }
  48.  
  49.               num1 = num2 = 0;
  50.           }
  51.  
  52. [ \t]     ;
  53.  
  54. .          {
  55.               printf("Invalid character\n");
  56.            }
  57. %%
  58.  
  59. int main()
  60. {
  61.     printf("Enter expression (Example: 10+20):\n");
  62.     yylex();
  63.     return 0;
  64. }
Success #stdin #stdout #stderr 0.02s 6828KB
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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/hK2UHz/prog:4:1: Syntax error: Operator expected
ERROR: /home/hK2UHz/prog:64:0: Syntax error: Unexpected end of file
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/wsHjNW
language:
Prolog (swi 7.6.4)
created:
55 minutes ago
visibility:
public

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