Lexical 2

#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>

bool isKeyword(char *str, int left, int right)
{
    int state = 1;
    while (left <= right)
    {

        switch (state)
        {
        case 1:
            if (str[left] == 'i')
            {
                state = 2;
                break;
            }

        case 2:
            if (str[left] == 'f')
            {
                state = 3;
                break;
            }
        case 3:
            if (str[left] == ' ')
            {
                state = 4;
                break;
            }
        case 4:
            printf("%s", "Token issued is <if>\n");
            return true;
        }
        left += 1;
    }
    return (false);
};

bool isIdentifier(char *str, int left, int right)
{
    int state = 1;
    while (left <= right)
    {

        switch (state)
        {
        case 1:
            if (str[left] == 'x')
            {
                state = 2;
                break;
            }

        case 2:
            if (!isalnum(str[left]))
            {
                state = 3;
                break;
            }

        case 3:
            printf("%s", "Token issued is <id, x>\n");
            return true;
        }
        left += 1;
    }

    return false;
}

bool isNumber(char *str, int left, int right)
{
    int state = 1;
    while (left <= right)
    {

        char *token = "";
        switch (state)
        {
        case 1:
            if (
                str[left] == '3')
            {
                token += '3';
                state = 2;
                break;
            }

        case 2:
            if (str[left] == '0')
            {
                token += '0';
                state = 2;
                 break;
            }
            else
            {
                state = 3;
                 break;
            }

        case 3:
            printf("Token issued is <%s>\n", token);
            return true;
        }
        left += 1;
    }

    return (false);
}

bool isRelOp(char *str, int left, int right)
{
    int state = 1;
    while (left <= right)
    {

        switch (state)
        {
        case 1:
            if (str[left] == '>')
            {
                state = 2;
                 break;
            }

        case 2:
            printf("%s", "Token issued is <RELOP, GT>\n");
            return true;
        }
        left += 1;
    }
    return false;
}

bool isParentheses(char *str, int left, int right)
{
    int state = 1;
    while (left <= right)
    {

        switch (state)
        {
        case 1:
            if (str[left] == '(')
            {
                state = 2;
                 break;
            }
            else if (str[left] == ')')
            {
                state = 3;
                 break;
            }

        case 2:
            printf("%s", "Token issued is <PAREN, OPEN>\n");
            return true;

        case 3:
            printf("%s", "Token issued is <PAREN, close>\n");
            return true;
        }
        left += 1;
    }
    return false;
}
bool isWhiteSpace(char *str, int left, int right)
{
    int state = 1;
    while (left <= right)
    {

        switch (state)
        {
        case 1:
            if (str[left] == ' ')
            {
                state = 2;
                 break;
            }

        case 2:
            printf("%s", "Whitespace token not issued <>\n");
            return true;
        }
        left += 1;
    }
    return false;
}
int main()
{
    /* code */
    char str[20];
    printf("Enter input : ");
    gets(str);
    // printf("All Tokens are : \n");
    printf("%s\n", str);
    int left = 0, right = 0;
    int len = strlen(str);
    // printf("%d",len);
    while (right <= len && left <= right)
    {
        // printf("%s", str);
        // printf("%d", left);
        // printf("%d", right);

        if (isKeyword(str, left, right))
        {
            // left forward retract
            left = right;
            right -= 1;
        }
        else if (isIdentifier(str, left, right))
        {
            left = right;
            right -= 1;
        }
        else if (isNumber(str, left, right))
        {
            left = right;
            right -= 1;
        }
        else if (isRelOp(str, left, right))
        {
            left = right;
            right -= 1;
        }
        else if (isParentheses(str, left, right))
        {
            left = right;
            right -= 1;
        }
        else if (isWhiteSpace(str, left, right))
        {
            left = right;
            right -= 1;
        }
        else
        {
            left = right;
            right -= 1;
        }
        right += 1;
    }
    return 0;
}