feat(int_interval_extension): allow compound intervals in `fromSemito…

…nes` (#67) * feat(int_interval_extension): allow compound intervals in `fromSemitones` * refactor(int_interval_extension): simplify octaves calc
albertms10 · Apr 23, 2023 · 14a33c0 · 14a33c0
1 parent 9cd7211
commit 14a33c0
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Showing 2 changed files with 26 additions and 10 deletions.
diff --git a/lib/src/interval/int_interval_extension.dart b/lib/src/interval/int_interval_extension.dart
@@ -22,14 +22,21 @@ extension IntIntervalExtension on int {
   /// IntIntervalExtension.fromSemitones(12) == 8
   /// IntIntervalExtension.fromSemitones(4) == null
   /// ```
-  static int? fromSemitones(int semitones) =>
-      _intervalsToSemitonesDelta.keys.firstWhereOrNull(
-        (interval) =>
-            (semitones == chromaticDivisions
-                ? chromaticDivisions
-                : semitones.chromaticMod) ==
-            _intervalsToSemitonesDelta[interval],
-      );
+  static int? fromSemitones(int semitones) {
+    final size = _intervalsToSemitonesDelta.keys.firstWhereOrNull(
+      (interval) =>
+          (semitones == chromaticDivisions
+              ? chromaticDivisions
+              : semitones.chromaticMod) ==
+          _intervalsToSemitonesDelta[interval],
+    );
+    if (size == null) return null;
+    if (semitones == 12) return size;
+
+    final octaves = semitones ~/ chromaticDivisions;
+
+    return size + (octaves * 7);
+  }
 
   /// Returns the number of semitones of this [int] for a perfect interval or a
   /// minor interval, where appropriate.

diff --git a/test/src/interval/int_interval_extension_test.dart b/test/src/interval/int_interval_extension_test.dart
@@ -7,6 +7,9 @@ void main() {
       test(
         'should return the int interval with the corresponding semitones',
         () {
+          expect(IntIntervalExtension.fromSemitones(-5), 5);
+          expect(IntIntervalExtension.fromSemitones(-4), 6);
+          expect(IntIntervalExtension.fromSemitones(-2), 7);
           expect(IntIntervalExtension.fromSemitones(0), 1);
           expect(IntIntervalExtension.fromSemitones(1), 2);
           expect(IntIntervalExtension.fromSemitones(3), 3);
@@ -15,8 +18,14 @@ void main() {
           expect(IntIntervalExtension.fromSemitones(8), 6);
           expect(IntIntervalExtension.fromSemitones(10), 7);
           expect(IntIntervalExtension.fromSemitones(12), 8);
-          expect(IntIntervalExtension.fromSemitones(13), 2);
-          expect(IntIntervalExtension.fromSemitones(-2), 7);
+          expect(IntIntervalExtension.fromSemitones(13), 9);
+          expect(IntIntervalExtension.fromSemitones(15), 10);
+          expect(IntIntervalExtension.fromSemitones(17), 11);
+          expect(IntIntervalExtension.fromSemitones(19), 12);
+          expect(IntIntervalExtension.fromSemitones(20), 13);
+          expect(IntIntervalExtension.fromSemitones(22), 14);
+          expect(IntIntervalExtension.fromSemitones(24), 15);
+          expect(IntIntervalExtension.fromSemitones(36), 22);
         },
       );