Implementation of LEXICAL ANALYZER for IF STATEMENT with the help of Lex Tool in CPP

 Implementation of  LEXICAL ANALYZER for IF STATEMENT with  the help of Lex  Tool in CPP-

Program-

#include<iostream>

#include<fstream>

#include<stdlib.h>

#include<string.h>

#include<ctype.h>

using namespace std;

int isKeyword(char buffer[]) {

  char keywords[32][10] = {

    "auto",

    "break",

    "case",

    "char",

    "const",

    "continue",

    "default",

    "do",

    "double",

    "else",

    "enum",

    "extern",

    "float",

    "for",

    "goto",

    "if",

    "int",

    "long",

    "register",

    "return",

    "short",

    "signed",

    "sizeof",

    "static",

    "struct",

    "switch",

    "typedef",

    "union",

    "unsigned",

    "void",

    "volatile",

    "while"

  };

  int i, flag = 0;

  for (i = 0; i < 32; ++i) {

    if (strcmp(keywords[i], buffer) == 0) {

      flag = 1;

      break;

    }

  }

  return flag;

}

int main() {

  char ch, buffer[15], operators[] = "+-*/%=";

  ifstream fin("program.txt");

  int i, j = 0;

  if (!fin.is_open()) {

    cout << "error while opening the file\n";

    exit(0);

  }

  while (!fin.eof()) {

    ch = fin.get();

    for (i = 0; i < 6; ++i) {

      if (ch == operators[i])

        cout << ch << " is operator\n";

    }

    if (isalnum(ch)) {

      buffer[j++] = ch;

    } else if ((ch == ' ' || ch == '\n') && (j != 0)) {

      buffer[j] = '\0';

      j = 0;

      if (isKeyword(buffer) == 1)

        cout << buffer << " is keyword\n";

      else

        cout << buffer << " is indentifier\n";

    }

  }

  fin.close();

  return 0;

}