calcArith

//
// Created by Ait Rami on 1/26/2019.
//
float calcArith(char *_exp);

char *expressionToParse;

char peek()
{
    return *expressionToParse;
}

char get()
{
    return *expressionToParse++;
}

float expression();

float number()
{
    float result = get() - '0';
    while (peek() >= '0' && peek() <= '9')
    {
        result = 10*result + get() - '0';
    }
    return result;
}

float factor()
{
    if (peek() >= '0' && peek() <= '9')
        return number();
    else if (peek() == '(')
    {
        get(); // '('
        float result = expression();
        get(); // ')'
        return result;
    }
    else if (peek() == '-')
    {
        get();
        return -factor();
    }
    return 0; // error
}

float term()
{
    float result = factor();
    while (peek() == '*' || peek() == '/')
        if (get() == '*')
            result *= factor();
        else
            result /= factor();
    return result;
}

float expression()
{
    float result = term();
    while (peek() == '+' || peek() == '-')
        if (get() == '+')
            result += term();
        else
            result -= term();
    return result;
}

float calcArith(char* _exp) {
    expressionToParse=calloc(80, sizeof(char));
    strcpy(expressionToParse,_exp);
    //printf("%s",expressionToParse);
    return expression();
}