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  1. #include <stdio.h>
  2. #include <ctype.h>
  3. #include <string.h>
  4.  
  5. int main() {
  6.     char ch, str[20];
  7.     FILE *fp = fopen("input.c", "r");
  8.     if (!fp) return 1;
  9.  
  10.     while ((ch = fgetc(fp)) != EOF) {
  11.         if (isalpha(ch)) { // identifier or keyword
  12.             int i = 0;
  13.             str[i++] = ch;
  14.             while (isalnum(ch = fgetc(fp))) str[i++] = ch;
  15.             str[i] = '\0';
  16.             fseek(fp, -1, SEEK_CUR);
  17.             printf("Identifier: %s\n", str);
  18.         }
  19.         else if (isdigit(ch)) { // constant
  20.             int i = 0;
  21.             str[i++] = ch;
  22.             while (isdigit(ch = fgetc(fp)) || ch == '.') str[i++] = ch;
  23.             str[i] = '\0';
  24.             fseek(fp, -1, SEEK_CUR);
  25.             printf("Constant: %s\n", str);
  26.         }
  27.         else if (ch == '/' && (ch = fgetc(fp)) == '/') { // single-line comment
  28.             printf("Comment: //");
  29.             while ((ch = fgetc(fp)) != '\n') putchar(ch);
  30.             printf("\n");
  31.         }
  32.         else if (ch == '+' || ch == '-' || ch == '*' || ch == '/' || ch == '=')
  33.             printf("Operator: %c\n", ch);
  34.     }
  35.  
  36.     fclose(fp);
  37.     return 0;
  38. }
  39.  
Success #stdin #stdout #stderr 0.03s 6872KB
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Standard input is empty
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Standard output is empty
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ERROR: /home/W2FqDl/prog:38:1: Syntax error: end_of_file_in_quasi_quotation
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/q01b6A
language:
Prolog (swi 7.6.4)
created:
5 hours ago
visibility:
public

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