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  1. /* With Left Recursion
  2. E -> E+T | T
  3. T -> T*F | F
  4. F -> (E) | id
  5. */
  6. #include <ctype.h>
  7. #include <stdio.h>
  8. #include <stdlib.h>
  9. #include <string.h>
  10. char input[10];
  11. int i, error;
  12. void E();
  13. void T();
  14. void Eprime();
  15. void Tprime();
  16. void F();
  17. main() {
  18. printf("\nGrammar without left recursion");
  19. printf("\n\t\t E->TE' \n\t\t E'->+TE'|e \n\t\t T->FT' ");
  20. printf("\n\t\t T'->*FT'|e \n\t\t F->(E)|i");
  21. while (1) {
  22.  i = 0;
  23.  error = 0;
  24.  printf("Enter an arithmetic expression : "); // Eg: a+a*a
  25.  gets(input);
  26.  E();
  27.  if (strlen(input) == i && error == 0)
  28.  printf("\nAccepted..!!!\n");
  29.  else {
  30.  printf("\nRejected..!!!\n");
  31.  exit(0);
  32.  }
  33. }
  34. }
  35. void E() {
  36. T();
  37. Eprime();
  38. }
  39. void Eprime() {
  40. if (input[i] == '+') {
  41.  i++;
  42.  T();
  43.  Eprime();
  44. }
  45. }
  46. void T() {
  47. F();
  48. Tprime();
  49. }
  50. void Tprime() {
  51. if (input[i] == '*') {
  52.  i++;
  53.  F();
  54.  Tprime();
  55. }
  56. }
  57. void F() {
  58. if (isalnum(input[i]))
  59.  i++;
  60. 15. Recursive descent parser
  61. 25
  62. else if (input[i] == '(') {
  63.  i++;
  64.  E();
  65.  if (input[i] == ')')
  66.  i++;
  67.  else
  68.  error = 1;
  69. }
  70. else
  71.  error = 1;
  72. }
Success #stdin #stdout #stderr 0.02s 6984KB
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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/gJ3HOF/prog:6:1: Syntax error: Operator expected
ERROR: /home/gJ3HOF/prog:72:0: Syntax error: Unexpected end of file
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/ImOxSA
language:
Prolog (swi 7.6.4)
created:
2 days ago
visibility:
public

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