✨ feat(interval): add respellBySize method (#195)

albertms10 · Jun 21, 2023 · ecc33fe · ecc33fe
1 parent df80288
commit ecc33fe
Show file tree

Hide file tree

Showing 2 changed files with 34 additions and 0 deletions.
diff --git a/lib/src/interval/interval.dart b/lib/src/interval/interval.dart
@@ -208,6 +208,19 @@ final class Interval implements Comparable<Interval> {
   /// ```
   Interval get simplified => Interval._(size.simplified, quality);
 
+  /// Returns this [Interval] respelled by [size] while keeping the same
+  /// number of [semitones].
+  ///
+  /// Example:
+  /// ```dart
+  /// Interval.A4.respellBySize(5) == Interval.d5
+  /// Interval.d3.respellBySize(2) == Interval.M2
+  /// ```
+  Interval respellBySize(int size) => Interval._(
+        size,
+        Quality.fromInterval(size, semitones.abs() - size.semitones.abs()),
+      );
+
   /// Returns the iteration distance of this [Interval] between [note1] and
   /// [note2].
   ///

diff --git a/test/src/interval/interval_test.dart b/test/src/interval/interval_test.dart
@@ -292,6 +292,27 @@ void main() {
       });
     });
 
+    group('.respellBySize()', () {
+      test('should return this Interval respelled by size', () {
+        expect(Interval.A4.respellBySize(5), Interval.d5);
+        expect(Interval.d5.respellBySize(4), Interval.A4);
+        expect(Interval.M2.respellBySize(3), Interval.d3);
+        expect(
+          Interval.M3.respellBySize(5),
+          const Interval.perfect(5, PerfectQuality.triplyDiminished),
+        );
+        expect(Interval.P1.respellBySize(2), Interval.d2);
+        expect(Interval.m2.respellBySize(1), Interval.A1);
+
+        expect((-Interval.M3).respellBySize(-4), -Interval.d4);
+        expect((-Interval.d5).respellBySize(-4), -Interval.A4);
+        expect(
+          (-Interval.P4).respellBySize(-5),
+          const Interval.perfect(-5, PerfectQuality.doublyDiminished),
+        );
+      });
+    });
+
     group('.circleFrom()', () {
       test('should return the circle of this Interval', () {
         expect(Interval.P5.circleFrom(Note.c, distance: 0), const [Note.c]);