helpers.c

// Helper functions for music

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

int findOctave(char);

// Converts a fraction formatted as X/Y to eighths
int duration(string fraction)
{
    int num = atoi(&fraction [0]);
    int den = atoi(&fraction [2]);
    int durvalue = num * 8 / den;
    return durvalue;
}

// Calculates frequency (in Hz) of a note
int frequency(string note)
{
    // TODO
    int freqvalue = 440; // count notes from A4 = 440 Hz
    char rootnote = note [0];
    int semitones = 0; // set starting note = A4
    int octave = 4;
    bool isFlat = false;
    bool isSharp = false;
    char sf = note [1];

    // test for sharp/flat, then find the octave named in the string
    if (sf == '#')
    {
        isSharp = true;
        octave = findOctave(note [2]);
    }
    else if (sf == 'b')
    {
        isFlat = true;
        octave = findOctave(note [2]);
    }
    else
    {
        octave = findOctave(note [1]);
    }

    // use rootnote, sharp/flat, and octave to calculate semitone distance
    switch (rootnote)
    {
        case 'A' :
            // do nothing
            break;
        case 'B' :
            semitones = semitones + 2;
            break;
        case 'C' :
            semitones = semitones - 9;
            break;
        case 'D' :
            semitones = semitones - 7;
            break;
        case 'E' :
            semitones = semitones - 5;
            break;
        case 'F' :
            semitones = semitones - 4;
            break;
        case 'G' :
            semitones = semitones - 2;
            break;
    }
    if (isSharp)
    {
        semitones++;
    }
    if (isFlat)
    {
        semitones--;
    }
    // adjust for octave
    semitones = semitones + ((octave - 4) * 12);

    // calculate frequency value

    double freq = 440 * pow(2.0, ((double) semitones / 12.0));
    freqvalue = (int) round(freq);
    return freqvalue;
}

// Used by frequency to determine octave represented by a one-character string containing a number
int findOctave(char octletr)
{
    int coctave = atoi(&octletr);
    return coctave;
}

// Determines whether a string represents a rest
bool is_rest(string s)
{
    if (strcmp(s, "") == 0)
    {
        return true;
    }
    else
    {
        return false;
    }
}