Implement arithmetically accumulative repetition

ref #281

README.md

@@ -17,6 +17,8 @@ The `sonic-weave` package is many things.
 
 You may also be interested in the [technical overview](https://github.com/xenharmonic-devs/sonic-weave/blob/main/documentation/technical.md) of SonicWeave as a programming language.
 
+Appendix: [tempering](https://github.com/xenharmonic-devs/sonic-weave/blob/main/documentation/tempering.md), [commas](https://github.com/xenharmonic-devs/sonic-weave/blob/main/documentation/commas.md)
+
 ## Highlights
 Harmonic segment from the 8th harmonic to the 16th (repeating at the octave).
 ```c

documentation/BUILTIN.md

@@ -659,6 +659,12 @@ Stack the current scale on top of itself. Clears the scale if the number of repe
 ### repeated(*times = 2*, *scale = $$*)
 Stack the current/given scale on top of itself.
 
+### repeatedLinear(*times = 2*, *scale = $$*)
+Repeat the current/given scale shifted linearly each time.
+
+### repeatLinear(*times = 2*, *scale = $$*)
+Repeat the current/given scale shifted linearly each time. Clears the scale if the number of repeats is zero.
+
 ### replace(*interval*, *replacement*, *scale = $$*)
 Replace occurences of `interval` in the current/given scale by `replacement`.
 

documentation/advanced-dsl.md

@@ -207,7 +207,7 @@ See [BUILTIN.md](https://github.com/xenharmonic-devs/sonic-weave/blob/main/docum
 
 ### Highlights
 
-Many helper functions have an arithmetic and geometric variants.
+Many helper functions have arithmetic and geometric variants.
 
 | Action           | Linear           | Logarithmic    | Logarithmic (accumulative)    |
 | ---------------- | ---------------- | -------------- | ----------------------------- |
@@ -217,6 +217,8 @@ Many helper functions have an arithmetic and geometric variants.
 | Stacking         | `stackLinear()`  | `stack()`      | *N/A*                         |
 | Repeating        | `flatRepeat()`   | `flatRepeat()` | `repeat()`                    |
 
+There's also the linearly accumulating `repeatLinear()` for repeating harmonic segments arithmetically.
+
 ## Issues with the decimal separator
 To be backwards compatible with Scale Workshop versions 1 and 2, SonicWeave preserves the syntax for "dot cents" and "comma decimals".
 

src/parser/__tests__/stdlib.spec.ts

@@ -1417,4 +1417,29 @@ describe('SonicWeave standard library', () => {
       'An interval is required.'
     );
   });
+
+  it('can repeat harmonics linearly (fifth to octave)', () => {
+    const scale = expand('6:7:9;repeatLinear()');
+    expect(scale).toEqual(['7/6', '9/6', '10/6', '12/6']);
+  });
+
+  it('can repeat harmonics linearly (octave to double octave)', () => {
+    const scale = expand('3:5:6;repeatLinear(3)');
+    expect(scale).toEqual(['5/3', '6/3', '8/3', '9/3', '11/3', '12/3']);
+  });
+
+  it('can repeat JI linearly (fourth to octave)', () => {
+    const scale = expand('10/9;7/6;4/3;repeatLinear(3)');
+    expect(scale).toEqual([
+      '10/9',
+      '7/6',
+      '4/3',
+      '13/9',
+      '9/6',
+      '5/3',
+      '16/9',
+      '11/6',
+      '6/3',
+    ]);
+  });
 });

src/stdlib/prelude.ts

@@ -772,9 +772,8 @@ riff rotated(onto = 1, scale = $$) {
 
 riff repeated(times = 2, scale = $$) {
   "Stack the current/given scale on top of itself.";
-  if (not times) {
+  if (not times)
     return [];
-  }
   scale;
   const equave = scale[-1];
   for (const level of equave ~^ [1..times-1])
@@ -790,6 +789,25 @@ riff repeat(times = 2, scale = $$) {
   return;
 }
 
+riff repeatedLinear(times = 2, scale = $$) {
+  "Repeat the current/given scale shifted linearly each time.";
+  if (not times)
+    return [];
+  scale;
+  const total = (scale[-1] ~- 1);
+  for (const level of total ~* [1..times-1])
+    (scale ~- 1) ~+ level ~+ 1;
+}
+
+riff repeatLinear(times = 2, scale = $$) {
+  "Repeat the current/given scale shifted linearly each time. Clears the scale if the number of repeats is zero.";
+  $ = scale;
+  const segment = $[..];
+  clear();
+  repeatedLinear(times, segment);
+  return;
+}
+
 riff flatRepeat(times = 2, scale = $$) {
   "Repeat the current/given intervals as-is without accumulating equaves. Clears the scale if the number of repeats is zero.";
   $ = scale;