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  1. /*lex program to implement 
  2. 		- a simple calculator.*/
  3.  
  4. % { 
  5. int op = 0,i; 
  6. float a, b; 
  7. % } 
  8.  
  9. dig [0-9]+|([0-9]*)"."([0-9]+) 
  10. add "+"
  11. sub "-"
  12. mul "*"
  13. div "/"
  14. pow "^"
  15. ln \n 
  16. %% 
  17.  
  18. /* digi() is a user defined function */
  19. {dig} {digi();} 
  20. {add} {op=1;} 
  21. {sub} {op=2;} 
  22. {mul} {op=3;} 
  23. {div} {op=4;} 
  24. {pow} {op=5;} 
  25. {ln} {printf("\n The Answer :%f\n\n",a);} 
  26.  
  27. %% 
  28. digi() 
  29. { 
  30. if(op==0) 
  31.  
  32. /* atof() is used to convert 
  33. 	- the ASCII input to float */
  34. a=atof(yytext); 
  35.  
  36. else
  37. { 
  38. b=atof(yytext); 
  39.  
  40. switch(op) 
  41. { 
  42. case 1:a=a+b; 
  43. 	break; 
  44.  
  45. case 2:a=a-b; 
  46. break; 
  47.  
  48. case 3:a=a*b; 
  49. break; 
  50.  
  51. case 4:a=a/b; 
  52. break; 
  53.  
  54. case 5:for(i=a;b>1;b--) 
  55. a=a*i; 
  56. break; 
  57. } 
  58. op=0; 
  59. } 
  60. } 
  61.  
  62. main(int argv,char *argc[]) 
  63. { 
  64. yylex(); 
  65. } 
  66.  
  67. yywrap() 
  68. { 
  69. return 1; 
  70. } 
  71.  
Success #stdin #stdout #stderr 0.04s 6852KB
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Standard input is empty
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Standard output is empty
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ERROR: /home/RY6n1K/prog:70:2: Syntax error: Unexpected end of file
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/HWEmK3
language:
Prolog (swi 7.6.4)
created:
12 days ago
visibility:
public

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