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Add signature method for a scale. Closes #89 #91

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5 changes: 5 additions & 0 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -181,6 +181,8 @@ The chroma number is ranging from pitch class C which is 0 to 11 which is B
#### Note#interval(interval)
- A sugar function for calling teoria.interval(note, interval);

Returns a new note based on the passed interval.
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This comment isn't related the the PR. Please remove it.


Look at the documentation for `teoria.interval`

#### Note#transpose(interval)
Expand Down Expand Up @@ -415,6 +417,9 @@ scale step. E.g. 'first', 'second', 'fourth', 'seventh'.

*showOctaves* - A boolean meaning the same as `showOctaves` in `Note#solfege`

#### Scale#signature()
- Returns the sequence of notes representing the key signature of a scale
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If you could add an example of how to use it, and which values the method returns, that'd be great!



## teoria.interval(from, to)
- A sugar function for the `#from` and `#between` methods of the same namespace and
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26 changes: 26 additions & 0 deletions lib/scale.js
Original file line number Diff line number Diff line change
Expand Up @@ -102,6 +102,32 @@ Scale.prototype = {
this.tonic = scale.tonic;

return this;
},

/**
* Get the sequence of notes representing key signature of a scale, in proper order.
* There are two possible signatures for any scale: flats and sharps.
* Sharps signature is got by traversing notes by P5 intervals to the right
* till all the notes of the scale are covered.
* Flats signature is got by traversing by P4 intervals to the left in the same manner, which is equal to reversed sharps.
*/
signature: function() {
var sequence = this.notes().sort(function (a, b) {
var aCoord = a.coord[1] < 0 ? a.coord[1] + 12 : a.coord[1];
var bCoord = b.coord[1] < 0 ? b.coord[1] + 12 : b.coord[1];
return aCoord - bCoord;
});

//if at least one flat - return flats signature
if (sequence.some(function (note) {
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If you could maybe break this into two lines (a bit more descriptive):

var hasFlat = sequence.some(function (note) {
  return note.accidentalValue() < 0;
});

if (hasFlat) { ... }

return note.accidentalValue() < 0;
})) {
sequence = sequence.reverse();
}

return sequence.filter(function (note) {
return note.accidentalValue() !== 0;
});
}
};

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12 changes: 12 additions & 0 deletions test/scales.js
Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,18 @@ vows.describe('Scales').addBatch({
assert.deepEqual(note.scale('chromatic').simple(),
["ab", "bbb", "bb", "cb", "c", "db",
"d", "eb", "fb", "f", "gb", "g"]);
},

'Signature': function(note) {
function name (note) {return note.name() + note.accidental() }

assert.equal(teoria.note('f#').scale('major').signature().map(name).toString(), 'f#,c#,g#,d#,a#,e#');
assert.equal(teoria.note('db').scale('major').signature().map(name).toString(), 'bb,eb,ab,db,gb');

assert.equal(teoria.note('c').scale('major').signature().map(name).toString(), '');
assert.equal(teoria.note('a').scale('minor').signature().map(name).toString(), '');
assert.equal(teoria.note('d').scale('major').signature().map(name).toString(), 'f#,c#');
assert.equal(teoria.note('b').scale('minor').signature().map(name).toString(), 'f#,c#');
}
}
}).export(module);