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  1. #include <stdio.h>
  2. #include <ctype.h>
  3. #include <string.h>
  4.  
  5.  
  6. typedef struct
  7. {
  8.     char lexeme[100];
  9.     char type[20];
  10. } Token;
  11.  
  12.  
  13. const char* keywords[] = {"int","float","if","else","while","return","void","char","for","double"};
  14. const int num_keywords = sizeof(keywords) / sizeof(keywords[0]);
  15.  
  16.  
  17. int isKeyword(const char* token)
  18. {
  19.     for (int i = 0; i < num_keywords; i++)
  20.     {
  21.         if (strcmp(token, keywords[i]) == 0)
  22.             return 1;
  23.     }
  24.     return 0;
  25. }
  26.  
  27.  
  28. Token classifyToken(const char *token)
  29. {
  30.     Token t;
  31.     strcpy(t.lexeme, token);
  32.  
  33.     if (isKeyword(token))
  34.         strcpy(t.type, "KEYWORD");
  35.  
  36.     else if (isdigit(token[0]))
  37.         strcpy(t.type, "NUMBER");
  38.  
  39.     else if (isalpha(token[0]) || token[0] == '_')
  40.         strcpy(t.type, "IDENTIFIER");
  41.  
  42.     else if (strchr("+-*/=<>!", token[0]))
  43.         strcpy(t.type, "OPERATOR");
  44.  
  45.     else if (strchr(";(),{}", token[0]))
  46.         strcpy(t.type, "DELIMITER");
  47.  
  48.     else
  49.         strcpy(t.type, "UNKNOWN");
  50.  
  51.     return t;
  52. }
  53.  
  54.  
  55. void lexicalAnalyzer(const char *input)
  56. {
  57.     char token[100];
  58.     int index = 0;
  59.  
  60.     for (int i = 0; i < strlen(input); i++)
  61.     {
  62.         char ch = input[i];
  63.  
  64.  
  65.         if (isspace(ch))
  66.         {
  67.             if (index > 0)
  68.             {
  69.                 token[index] = '\0';
  70.                 Token t = classifyToken(token);
  71.                 printf("%s: %s\n", t.type, t.lexeme);
  72.                 index = 0;
  73.             }
  74.         }
  75.  
  76.  
  77.         else if (strchr("+-*/=<>!", ch))
  78.         {
  79.             if (index > 0)
  80.             {
  81.                 token[index] = '\0';
  82.                 Token t = classifyToken(token);
  83.                 printf("%s: %s\n", t.type, t.lexeme);
  84.                 index = 0;
  85.             }
  86.  
  87.  
  88.             if (input[i+1] == '=')
  89.             {
  90.                 token[0] = ch;
  91.                 token[1] = '=';
  92.                 token[2] = '\0';
  93.  
  94.                 Token t = classifyToken(token);
  95.                 printf("%s: %s\n", t.type, t.lexeme);
  96.  
  97.                 i++; 
  98.             }
  99.             else
  100.             {
  101.                 token[0] = ch;
  102.                 token[1] = '\0';
  103.  
  104.                 Token t = classifyToken(token);
  105.                 printf("%s: %s\n", t.type, t.lexeme);
  106.             }
  107.         }
  108.  
  109.  
  110.         else if (strchr(";(),{}", ch))
  111.         {
  112.             if (index > 0)
  113.             {
  114.                 token[index] = '\0';
  115.                 Token t = classifyToken(token);
  116.                 printf("%s: %s\n", t.type, t.lexeme);
  117.                 index = 0;
  118.             }
  119.  
  120.             token[0] = ch;
  121.             token[1] = '\0';
  122.  
  123.             Token t = classifyToken(token);
  124.             printf("%s: %s\n", t.type, t.lexeme);
  125.         }
  126.  
  127.  
  128.         else
  129.         {
  130.             token[index++] = ch;
  131.         }
  132.     }
  133.  
  134.  
  135.     if (index > 0)
  136.     {
  137.         token[index] = '\0';
  138.         Token t = classifyToken(token);
  139.         printf("%s: %s\n", t.type, t.lexeme);
  140.     }
  141. }
  142.  
  143. int main()
  144. {
  145.     char input[200];
  146.  
  147.     printf("Enter a simple C code snippet: ");
  148.     fgets(input, sizeof(input), stdin);
  149.  
  150.     printf("\nTokens Found:\n");
  151.     lexicalAnalyzer(input);
  152.  
  153.     return 0;
  154. }
Success #stdin #stdout 0s 5308KB
comments (?)
stdin
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int a +=b
stdout
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Enter a simple C code snippet: 
Tokens Found:
KEYWORD: int
IDENTIFIER: a
OPERATOR: +=
IDENTIFIER: b
https://ideone.com/1qsHeu
language:
C (gcc 8.3)
created:
19 hours ago
visibility:
public

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