CS50/PSET3/helpers.c

// Helper functions for music

#include <cs50.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>

#include "helpers.h"

// Converts a fraction formatted as X/Y to eighths
int duration(string fraction)
{
    // TODO
    if (fraction[0] == '1')
    {
        if (fraction[2] == '1')
        {
            return 8;
        }
        if (fraction[2] == '2')
        {
            return 4;
        }
        if (fraction[2] == '4')
        {
            return 2;
        }
        if (fraction[2] == '8')
        {
            return 1;
        }
    }
    else if (fraction[0] == '3' || fraction[0] == '8')
    {
        return 3;
    }
    else
    {
        return 0;
    }
    return 0;
}

// Calculates frequency (in Hz) of a note
int frequency(string note)
{
    //calculate
    double freq = 440.00; //hz
    int res;



    //which Octave
    int octave = note[strlen(note) - 1];
    octave -= 48;


    //Octave
    if (octave == 4)
    {
        freq *= 1;
    }
    else if (octave > 4)
    {
        double temp = octave - 4;
        freq = pow(2.00, temp) * 440.00; // or,  (2^(temp) * 440);
    }
    else if (octave < 4)
    {
        double temp = 4 - octave;
        freq = pow(2.00, temp) / 440.00; //or, (2^(temp) / 440);
    }

    //Note
    if (note[0] == 'A')
    {
        freq *= 1;
    }
    else if (note[0] == 'B')
    {
        freq *= pow(2.00, (2.00/12));
    }
    else if (note[0] == 'C')
    {
        freq /= pow(2.00, (9.00/12));
    }
    else if (note[0] == 'D')
    {
        freq /= pow(2.00, (7.00/12));
    }
    else if (note[0] == 'E')
    {
        freq /= pow(2.00, (5.00/12));
    }
    else if (note[0] == 'F')
    {
        freq /= pow(2.00, (4.00/12));
    }
    else if (note[0] == 'G')
    {
        freq /= pow(2.00, (2.00/12));
    }


    //Accidentals
    if (note[1] == '#')
    {
        freq *= (pow(2.0, (1.0 / 12.0)));
    }
    else if (note[1] == 'b')
    {
        freq /= (pow(2.0, (1.0 / 12.0)));
    }

    res = round(freq);

    return res;
}

// Determines whether a string represents a rest
bool is_rest(string s)
{
    // check if rest
    if (s == NULL)
    {
        return true;
    }
    else
    {
        return false;
    }
}