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💥 feat(tuning_system): generalize cents method expecting ratio instead of semitones #251

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merged 1 commit into from
Aug 6, 2023
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💥 feat(tuning_system): generalize cents method expecting ratio instead of semitones #251

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17 changes: 10 additions & 7 deletions lib/src/tuning/tuning_system.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -57,18 +57,21 @@ class EqualTemperament extends TuningSystem {
double ratio([int semitones = 1]) =>
math.pow(2, semitones / octaveDivisions).toDouble();

/// Returns the number of cents for [semitones] in this [EqualTemperament].
/// Returns the number of cents for [ratio] in this [EqualTemperament].
///
/// See [Cent](https://en.wikipedia.org/wiki/Cent_(music)).
///
/// Example:
/// ```dart
/// EqualTemperament.edo12.cents() == 100
/// EqualTemperament.edo12.cents(7) == 700
/// EqualTemperament.edo19.cents() == 63.16
/// var ratio = EqualTemperament.edo12.ratio;
/// EqualTemperament.edo12.cents(ratio()) == 100
/// EqualTemperament.edo12.cents(ratio(7)) == 700
///
/// ratio = EqualTemperament.edo19.ratio;
/// EqualTemperament.edo19.cents(ratio()) == 63.16
/// ```
double cents([int semitones = 1]) =>
math.log(ratio(semitones)) /
double cents(double ratio) =>
math.log(ratio) /
math.log(2) *
100 *
EqualTemperament.edo12.octaveDivisions;
Expand All @@ -90,6 +93,6 @@ class EqualTemperament extends TuningSystem {
semitonesUpToP5 += divisionEntry.value;
}

return cents(semitonesUpToP5);
return cents(ratio(semitonesUpToP5));
}
}
20 changes: 12 additions & 8 deletions test/src/tuning/tuning_system_test.dart
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Expand Up @@ -26,16 +26,20 @@ void main() {

group('.cents()', () {
test(
'should return the number of cents for semitones in this '
'EqualTemperament',
'should return the number of cents for ratio in this EqualTemperament',
() {
expect(EqualTemperament.edo12.cents(), closeTo(100, 0.01));
expect(EqualTemperament.edo12.cents(6), closeTo(600, 0.01));
expect(EqualTemperament.edo12.cents(12), closeTo(1200, 0.01));
var ratio = EqualTemperament.edo12.ratio;
expect(EqualTemperament.edo12.cents(ratio()), closeTo(100, 0.01));
expect(EqualTemperament.edo12.cents(ratio(6)), closeTo(600, 0.01));
expect(EqualTemperament.edo12.cents(ratio(12)), closeTo(1200, 0.01));

expect(EqualTemperament.edo19.cents(), closeTo(63.16, 0.01));
expect(EqualTemperament.edo19.cents(10), closeTo(631.58, 0.01));
expect(EqualTemperament.edo19.cents(19), closeTo(1200, 0.01));
ratio = EqualTemperament.edo19.ratio;
expect(EqualTemperament.edo19.cents(ratio()), closeTo(63.16, 0.01));
expect(
EqualTemperament.edo19.cents(ratio(10)),
closeTo(631.58, 0.01),
);
expect(EqualTemperament.edo19.cents(ratio(19)), closeTo(1200, 0.01));
},
);
});
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