From f858d89f7b1d8f2771cdfa6c4fb7e3c41272d014 Mon Sep 17 00:00:00 2001
From: Bradford Powell <bpow@unc.edu>
Date: Fri, 29 Jul 2022 18:54:53 -0400
Subject: [PATCH] implement random choice in mini notation

this will require update to krill-parser.js (aggregated
in later commit) to work properly
---
 packages/mini/krill.pegjs | 22 ++++++++++++++++------
 packages/mini/mini.mjs    |  9 +++++++++
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/packages/mini/krill.pegjs b/packages/mini/krill.pegjs
index e266c395..6302614d 100644
--- a/packages/mini/krill.pegjs
+++ b/packages/mini/krill.pegjs
@@ -8,6 +8,7 @@ This program is free software: you can redistribute it and/or modify it under th
 // a sequence = a serie of elements placed between quotes
 // a stack = a serie of vertically aligned slices sharing the same overall length
 // a slice = a serie of horizontally aligned elements
+// a choose = a serie of elements, one of which is chosen at random
 
 
 {
@@ -81,7 +82,8 @@ DIGIT  = [0-9]
 // ------------------ delimiters ---------------------------
 
 ws "whitespace" = [ \n\r\t]*
-comma = ws "," ws;
+comma = ws "," ws
+pipe = ws "|" ws
 quote = '"' / "'"
 
 // ------------------ steps and cycles ---------------------------
@@ -91,7 +93,7 @@ step_char =  [0-9a-zA-Z~] / "-" / "#" / "." / "^" / "_" / ":"
 step = ws chars:step_char+ ws { return chars.join("") }
 
 // define a sub cycle e.g. [1 2, 3 [4]]
-sub_cycle = ws  "[" ws s:stack ws "]" ws { return s}
+sub_cycle = ws  "[" ws s:stack_or_choose ws "]" ws { return s}
 
 // define a timeline e.g <1 3 [3 5]>. We simply defer to a stack and change the alignement
 timeline = ws "<" ws sc:single_cycle ws ">" ws
@@ -135,14 +137,22 @@ single_cycle = s:(slice_with_modifier)+
   { return new PatternStub(s,"h"); }
 
 // a stack is a serie of vertically aligned single cycles, separated by a comma
+stack_tail = tail:(comma @single_cycle)+
+  { return { alignment: 'v', list: tail }; }
+
+// a choose is a serie of pipe-separated single cycles, one of which is chosen
+// at random each time through the pattern
+choose_tail = tail:(pipe @single_cycle)+
+  { return { alignment: 'r', list: tail }; }
+
 // if the stack contains only one element, we don't create a stack but return the
 // underlying element
-stack = c:single_cycle cs:(comma v:single_cycle { return v})*
-  { if (cs.length == 0 && c instanceof Object) { return c;} else { cs.unshift(c); return new PatternStub(cs,"v");}  }
+stack_or_choose = head:single_cycle tail:(stack_tail / choose_tail)?
+  { if (tail && tail.list.length > 0) { return new PatternStub([head, ...tail.list], tail.alignment); } else { return head; } }
 
 // a sequence is a quoted stack
-sequence = ws quote s:stack quote
-  { return s; }
+sequence = ws quote sc:stack_or_choose quote
+  { return sc; }
 
 // ------------------ operators ---------------------------
 
diff --git a/packages/mini/mini.mjs b/packages/mini/mini.mjs
index 684616ff..2a7bd077 100644
--- a/packages/mini/mini.mjs
+++ b/packages/mini/mini.mjs
@@ -10,6 +10,12 @@ import { addMiniLocations } from '@strudel.cycles/eval/shapeshifter.mjs';
 
 const { pure, Pattern, Fraction, stack, slowcat, sequence, timeCat, silence, reify } = strudel;
 
+var _seedState = 0;
+
+function _nextSeed() {
+  return _seedState++;
+}
+
 const applyOptions = (parent) => (pat, i) => {
   const ast = parent.source_[i];
   const options = ast.options_;
@@ -84,6 +90,9 @@ export function patternifyAST(ast) {
       if (alignment === 'v') {
         return stack(...children);
       }
+      if (alignment === 'r') {
+        return strudel.chooseInWith(strudel.rand.early(0.0001 * _nextSeed()).segment(1), children);
+      }
       const weightedChildren = ast.source_.some((child) => !!child.options_?.weight);
       if (!weightedChildren && alignment === 't') {
         return slowcat(...children);