refactor(note): 💥 rewrite splitCircleOfFifths method to return `Ite…

…rable`s (#574)

Signed-off-by: Albert Mañosa <26429103+albertms10@users.noreply.github.com>

README.md

@@ -239,8 +239,10 @@ up to a distance:
 Interval.P5.circleFrom(Note.c).take(13).toList();
 // [C, G, D, A, E, B, F♯, C♯, G♯, D♯, A♯, E♯, B♯]
 Note.c.circleOfFifths(distance: 3); // [E♭, B♭, F, C, G, D, A]
-Note.c.splitCircleOfFifths();
-// (flats: [F, B♭, E♭, A♭, D♭, G♭], sharps: [G, D, A, E, B, F♯])
+Note.c.splitCircleOfFifths.down.take(6).toList();
+// [F, B♭, E♭, A♭, D♭, G♭]
+Note.c.splitCircleOfFifths.up.take(8).toList();
+// [G, D, A, E, B, F♯, C♯, G♯]
 
 Note.d.circleOfFifthsDistance; // 2
 Note.a.flat.circleOfFifthsDistance; // -4

example/main.dart

@@ -125,8 +125,10 @@ void main() {
   Interval.P5.circleFrom(Note.c).take(13).toList();
   // [C, G, D, A, E, B, F♯, C♯, G♯, D♯, A♯, E♯, B♯]
   Note.c.circleOfFifths(distance: 3); // [E♭, B♭, F, C, G, D, A]
-  Note.c.splitCircleOfFifths();
-  // (flats: [F, B♭, E♭, A♭, D♭, G♭], sharps: [G, D, A, E, B, F♯])
+  Note.c.splitCircleOfFifths.down.take(6).toList();
+  // [F, B♭, E♭, A♭, D♭, G♭]
+  Note.c.splitCircleOfFifths.up.take(8).toList();
+  // [G, D, A, E, B, F♯, C♯, G♯]
 
   Note.d.circleOfFifthsDistance; // 2
   Note.a.flat.circleOfFifthsDistance; // -4

lib/src/note/note.dart

@@ -300,38 +300,26 @@ final class Note extends Scalable<Note>
   /// ```
   Pitch inOctave(int octave) => Pitch(this, octave: octave);
 
-  /// The circle of fifths starting from this [Note] up to [distance],
-  /// split by `sharps` and `flats`.
+  /// The circle of fifths starting from this [Note] split by sharps (`up`) and
+  /// flats (`down`).
   ///
   /// Example:
   /// ```dart
-  /// Note.c.splitCircleOfFifths(distance: 4) == (
-  ///   sharps: [Note.g, Note.d, Note.a, Note.e],
-  ///   flats: [Note.f, Note.b.flat, Note.e.flat, Note.a.flat],
-  /// )
-  ///
-  /// Note.a.splitCircleOfFifths(distance: 4) == (
-  ///   sharps: [Note.e, Note.b, Note.f.sharp, Note.c.sharp],
-  ///   flats: [Note.d, Note.g, Note.c, Note.f],
-  /// )
+  /// Note.c.splitCircleOfFifths.up.take(6).toList()
+  ///   == [Note.g, Note.d, Note.a, Note.e, Note.b, Note.f.sharp]
+  ///
+  /// Note.c.splitCircleOfFifths.down.take(4).toList()
+  ///   == [Note.f, Note.b.flat, Note.e.flat, Note.a.flat]
+  ///
+  /// Note.a.splitCircleOfFifths.up.take(4).toList()
+  ///   == [Note.e, Note.b, Note.f.sharp, Note.c.sharp]
   /// ```
   /// ---
   /// See also:
   /// * [circleOfFifths] for a continuous list version of [splitCircleOfFifths].
-  ({List<Note> sharps, List<Note> flats}) splitCircleOfFifths({
-    int distance = chromaticDivisions ~/ 2,
-  }) =>
-      (
-        sharps: Interval.P5
-            .circleFrom(this)
-            .skip(1)
-            .take(distance.abs())
-            .toList(growable: false),
-        flats: Interval.P4
-            .circleFrom(this)
-            .skip(1)
-            .take(distance.abs())
-            .toList(growable: false),
+  ({Iterable<Note> up, Iterable<Note> down}) get splitCircleOfFifths => (
+        up: Interval.P5.circleFrom(this).skip(1),
+        down: Interval.P4.circleFrom(this).skip(1),
       );
 
   /// The continuous circle of fifths up to [distance] including this [Note],
@@ -359,9 +347,13 @@ final class Note extends Scalable<Note>
   /// * [splitCircleOfFifths] for a different representation of the same
   ///   circle of fifths.
   List<Note> circleOfFifths({int distance = chromaticDivisions ~/ 2}) {
-    final (:flats, :sharps) = splitCircleOfFifths(distance: distance);
+    final (:down, :up) = splitCircleOfFifths;
 
-    return [...flats.reversed, this, ...sharps];
+    return [
+      ...down.take(distance).toList().reversed,
+      this,
+      ...up.take(distance),
+    ];
   }
 
   /// The distance in relation to the circle of fifths.

test/src/note/note_test.dart

@@ -341,14 +341,14 @@ void main() {
       );
     });
 
-    group('.splitCircleOfFifths()', () {
+    group('.splitCircleOfFifths', () {
       test('returns the split circle of fifths from this Note', () {
-        var (:sharps, :flats) = Note.c.splitCircleOfFifths();
+        var (:up, :down) = Note.c.splitCircleOfFifths;
         expect(
-          sharps,
+          up.take(6),
           [Note.g, Note.d, Note.a, Note.e, Note.b, Note.f.sharp],
         );
-        expect(flats, [
+        expect(down.take(6), [
           Note.f,
           Note.b.flat,
           Note.e.flat,
@@ -357,9 +357,9 @@ void main() {
           Note.g.flat,
         ]);
 
-        (:sharps, :flats) = Note.a.splitCircleOfFifths(distance: 7);
+        (:up, :down) = Note.a.splitCircleOfFifths;
         expect(
-          sharps,
+          up.take(7),
           [
             Note.e,
             Note.b,
@@ -371,7 +371,7 @@ void main() {
           ],
         );
         expect(
-          flats,
+          down.take(7),
           [
             Note.d,
             Note.g,