double string_to_double(string * s) //convert string to double
{
    int dot = -1;
    bool negative = false;
    int start = 0;
    if(s->at(0) == '-')
    {
        negative = true;
        start = 1;
    }
    for(int i = 0; i < s->size(); i++)
    {
        if(s->at(i) == '.')
        {
            dot = i;
            break;
        }
    }
    if(dot == -1)
    {
        double value = 0;
        for(int i = start ; i < s->size(); i++)
        {
                value *= 10;
                value += ((double)s->at(i) - 48); //must -48 since the typecast converts the string to ascii, not allowed to use std algos
        }
        if(negative)
        {
            return (value*-1);
        }
        return value;
    }
    else
    {
        double value = 0;
        for(int i = start; i < dot; i++)
        {
            value *= 10;
            value += ((double)s->at(i) - 48.0); // must -48 since the typecase converts the string to ascii, not allowed tto use std algos
        }
        double decimal_value = 0.0;
        for(int i = s->size()-1; i > dot; i--)
        {
            decimal_value /= 10;
            decimal_value += ((double)s->at(i) - 48); // must -48 since the typecast converts the string to ascii, not allowed to use std algos
        }
        decimal_value /= 10; //the last division is still at the ones place
        if(negative)
        {
            return ((value + decimal_value)*-1);
        }
        return value + decimal_value;
    }
}