Lab 3

#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;
            }

        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 = 0;
    char ch;
    while (left <= right)
    {
        ch = str[left];
        switch (state)
        {
        case 0:
            if (isalpha(ch))
            {
                state = 1;
            }
            break;

        case 1:
            if (isalnum(ch))
            {
                state = 1;
                break;
            }

            else
            {
                state = 2;
            }

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

    return false;
}

bool isNumber(char *str, int left, int right)
{
    int state = 0;
    char token[20] = "";
    char ch;
    while (left <= right)
    {
        ch = str[left];
        switch (state)
        {
        case 0:
            if (isdigit(ch))
            {
                state = 1;
            }
            break;

        case 1:
            if (isdigit(ch))
            {
                strncat(token, &ch, 1);
                state = 1;
                break;
            }
            else if (ch == '.')
            {
                strncat(token, &ch, 1);
                state = 2;
                break;
            }
            else if (ch == 'E')
            {
                strncat(token, &ch, 1);
                state = 4;
                break;
            }
            else
            {
                state = 8;
            }

        case 2:
            if (isdigit(ch))
            {
                strncat(token, &ch, 1);
                state = 3;
            }
            break;
        case 3:
            if (isdigit(ch))
            {
                strncat(token, &ch, 1);
                state = 3;
            }
            else if (ch == 'E')
            {
                strncat(token, &ch, 1);
                state = 4;
            }
            else
            {
                state = 9;
            }
            break;
        case 4:
            if (ch == '+' || ch == '-')
            {
                strncat(token, &ch, 1);
                state = 5;
            }
            else if (isdigit(ch))
            {
                strncat(token, &ch, 1);
                state = 6;
            }
            break;
        case 5:
            if (isdigit(ch))
            {
                strncat(token, &ch, 1);
                state = 6;
            }

            break;
        case 6:
            if (isdigit(ch))
            {
                strncat(token, &ch, 1);
                state = 6;
                break;
            }
            else
            {
                state = 7;
            }

        case 7:

            printf("Token issued is <%s>\n", token);
            return true;
        case 8:
            printf("Token issued is <%s>\n", token);
            return true;
        case 9:
            printf("Token issued is <%s>\n", token);
            return true;
        }
        left += 1;
    }

    return (false);
}

bool isRelOp(char *str, int left, int right)
{
    int state = 0;
    while (left <= right)
    {

        switch (state)
        {
        case 0:
            if (str[left] == '<')
            {
                state = 1;
            }
            else if (str[left] == '>')
            {
                state = 6;
            }
            else if (str[left] == '=')
            {
                state = 5;
            }

            break;
        case 1:
            if (str[left] == '=')
            {
                state = 2;
            }
            else if (str[left] == '>')
            {
                state = 3;
            }
            else
            {
                printf("%s", "Token issued is <RELOP, LT>\n");
                return true;
            }
            break;
        case 2:
            printf("%s", "Token issued is <RELOP, LE>\n");
            return true;
        case 3:
            printf("%s", "Token issued is <RELOP, NE>\n");
            return true;
        case 5:
            printf("%s", "Token issued is <RELOP, EQ>\n");
            return true;
        case 6:
            if (str[left] == '=')
            {
                state = 7;
            }
            else
            {
                printf("%s", "Token issued is <RELOP, GT>\n");
                return true;
            }
            break;
        case 7:
            printf("%s", "Token issued is <RELOP, GE>\n");
            return true;
        }
        left += 1;
    }
    return false;
}

bool isParentheses(char *str, int left, int right)
{
    int state = 0;
    while (left <= right)
    {

        switch (state)
        {
        case 0:
            if (str[left] == '(')
            {
                state = 1;
            }

            else if (str[left] == ')')
            {
                state = 2;
            }
            else if (str[left] == '{')
            {
                state = 3;
            }
            else if (str[left] == '}')
            {
                state = 4;
            }
            else if (str[left] == '[')
            {
                state = 5;
            }
            else if (str[left] == ']')
            {
                state = 6;
            }
            break;

        case 1:
            printf("%s", "Token issued is <PAREN, SIMP_OPEN>\n");
            return true;
        case 2:
            printf("%s", "Token issued is <PAREN, SIMP_CLOSE>\n");
            return true;
        case 3:
            printf("%s", "Token issued is <PAREN, CURL_OPEN>\n");
            return true;
        case 4:
            printf("%s", "Token issued is <PAREN, CURL_CLOSE>\n");
            return true;
        case 5:
            printf("%s", "Token issued is <PAREN, SQ_OPEN>\n");
            return true;
        case 6:
            printf("%s", "Token issued is <PAREN, SQ_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)
    {

        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
        // {
        //     printf("%s", "Unrecognized lexeme. No token issued.\n");
        // }
        right += 1;
    }
    return 0;
}