Making a lexical Analyzer

Question

I\'m working with a Lexical Analyzer program right now and I\'m using Java. I\'ve been researching for answers on this problem but until now I failed to find any. Here\'s my

Answer 1

Write a program to make a simple lexical analyzer that will build a symbol table from given stream of chars. You will need to read a file named “input.txt” to collect all chars. For simplicity, input file will be a C/Java/Python program without headers and methods(body of the main progrm). Then you will identify all the numerical values, identifiers, keywords, math operators, logical operators and others[distinct]. See the example for more details. You can assume that, there will be a space after each keyword.

#include
    #include
    #include

    int main(){
    /* By Ashik Rabbani
    Daffodil International University,CSE43 */
    keyword_check();
    identifier_check();
    math_operator_check();
    logical_operator_check();
    numerical_check();
    others_check();


        return 0;
    }


    void math_operator_check()
    {

        char ch, string_input[15], operators[] = "+-*/%";
        FILE *fp;
        char tr[20];
        int i,j=0;

        fp = fopen("input.txt","r");

        if(fp == NULL){
            printf("error while opening the file\n");
            exit(0);
        }
       printf("\nMath Operators : ");
        while((ch = fgetc(fp)) != EOF){
               for(i = 0; i < 6; ++i){
                   if(ch == operators[i])
                       printf("%c ", ch);

               }
               }
                printf("\n");



        fclose(fp);
    }


    void logical_operator_check()
    {

        char ch, string_input[15], operators[] = "&&||<>";
        FILE *fp;
        char tr[20];
        int i,j=0;

        fp = fopen("input.txt","r");

        if(fp == NULL){
            printf("error while opening the file\n");
            exit(0);
        }
       printf("\nLogical Operators : ");
        while((ch = fgetc(fp)) != EOF){
               for(i = 0; i < 6; ++i){
                   if(ch == operators[i])
                       printf("%c ", ch);

               }
               }
                printf("\n");



        fclose(fp);
    }

    void numerical_check()
    {

        char ch, string_input[15], operators[] ={'0','1','2','3','4','5','6','7','8','9'};
        FILE *fp;

        int i,j=0;

        fp = fopen("input.txt","r");

        if(fp == NULL){
            printf("error while opening the file\n");
            exit(0);
        }
       printf("\nNumerical Values : ");
        while((ch = fgetc(fp)) != EOF){
               for(i = 0; i < 6; ++i){
                   if(ch == operators[i])
                       printf("%c ", ch);

               }
               }
                printf("\n");



        fclose(fp);
    }

    void others_check()
    {
        char ch, string_input[15], symbols[] = "(){}[]";
        FILE *fp;
        char tr[20];
        int i,j=0;

        fp = fopen("input.txt","r");

        if(fp == NULL){
            printf("error while opening the file\n");
            exit(0);
        }
       printf("\nOthers : ");
        while((ch = fgetc(fp)) != EOF){
               for(i = 0; i < 6; ++i){
                   if(ch == symbols[i])
                       printf("%c ", ch);

               }
               }
               printf("\n");



        fclose(fp);
    }

    void identifier_check()
    {
        char ch, string_input[15];
        FILE *fp;
    char    operators[] ={'0','1','2','3','4','5','6','7','8','9'};
        int i,j=0;

        fp = fopen("input.txt","r");

        if(fp == NULL){
            printf("error while opening the file\n");
            exit(0);
        }

        printf("\nIdentifiers : ");
        while((ch = fgetc(fp)) != EOF){

               if(isalnum(ch)){
                   string_input[j++] = ch;
               }
               else if((ch == ' ' || ch == '\n') && (j != 0)){
                       string_input[j] = '\0';
                       j = 0;

                       if(isKeyword(string_input) == 1)
                       {

                       }

                       else
                           printf("%s ", string_input);
               }

               }

                printf("\n");


        fclose(fp);
    }

    int isKeyword(char string_input[]){
        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], string_input) == 0){
                flag = 1;
                break;
            }
        }

        return flag;
    }

    void keyword_check()
    {

        char ch, string_input[15], operators[] = "+-*/%=";
        FILE *fp;
        char tr[20];
        int i,j=0;

        printf(" Token Identification using C \n By Ashik-E-Rabbani \n 161-15-7093\n\n");

        fp = fopen("input.txt","r");

        if(fp == NULL){
            printf("error while opening the file\n");
            exit(0);
        }

        printf("\nKeywords : ");
        while((ch = fgetc(fp)) != EOF){

               if(isalnum(ch)){
                   string_input[j++] = ch;
               }
               else if((ch == ' ' || ch == '\n') && (j != 0)){
                       string_input[j] = '\0';
                       j = 0;

                       if(isKeyword(string_input) == 1)
                           printf("%s ", string_input);

               }

               }

     printf("\n");


        fclose(fp);
    }