made "distribution" list selector case-sensitivity setting aware

HISTORY.md

@@ -37,6 +37,7 @@
     * changed the semantics of empty list-type slots to return a new empty list instead of "nothing"
     * improved browser resource management for graphics and sounds
     * changed long-form input dialog setting's behavior to automatically expand / collapse slot type view
+    * made "distribution" list selector case-sensitivity setting aware and optimized for atomic data
     * slightly optimized pen drawing performance when WARPed
     * removed multibranched conditional library (cases.xml), because IF is now variadic
     * updated audio comp library with a faster (hyper) version of the "Hz for secs" reporter
@@ -82,6 +83,7 @@
 * v9-rc7
 * blocks: replaced the variadic black "ladder" symbol with a white vertical ellipsis label
 * blocks: changed the semantics of empty list-type slots to return a new empty list instead of "nothing"
+* threads: made "distribution" list selector case-sensitivity setting aware
 
 ### 2023-07-11
 * blocks, symbols, gui: design overhaul of variadic input slots

src/threads.js

@@ -2280,7 +2280,18 @@ Process.prototype.reportListAttribute = function (choice, list) {
         return this.reportUniqueValues(list);
     case 'distribution':
         this.assertType(list, 'list');
-        return list.distribution();
+        if (list.canBeCSV()) {
+            if (Process.prototype.isCaseInsensitive) {
+                return list.map(row => row instanceof List ?
+                    row.map(cell =>
+                        cell.toLowerCase()
+                    )
+                    : row.toLowerCase()
+                ).distribution();
+            }
+            return list.distribution();
+        }
+        return this.reportDistribution(list);
     case 'sorted':
         this.assertType(list, 'list');
         return this.reportSorted(list);
@@ -2374,6 +2385,39 @@ Process.prototype.reportUniqueValues = function (list) {
     this.pushContext();
 };
 
+Process.prototype.reportDistribution = function (list) {
+    // answer a new list with an entry for each unique value and the
+    // number of its occurrences in the source list,
+    // interpolated so it can be interrupted by the user
+    // because snapEquals() can be a lot slower than identity comparison
+    var next, record;
+    if (this.context.accumulator === null) {
+        this.assertType(list, 'list');
+        this.context.accumulator = {
+            idx : 0,
+            target : []
+        };
+    }
+    if (this.context.accumulator.idx === list.length()) {
+        this.returnValueToParentContext(
+            new List(this.context.accumulator.target.map(row => new List(row)))
+        );
+        return;
+    }
+    this.context.accumulator.idx += 1;
+    next = list.at(this.context.accumulator.idx);
+
+    record = this.context.accumulator.target.find(row =>
+        snapEquals(row[0], next)
+    );
+    if (record !== undefined) {
+        record[1] += 1;
+    } else {
+        this.context.accumulator.target.push([next, 1]);
+    }
+    this.pushContext();
+};
+
 Process.prototype.reportSorted = function (data) {
     return new List(data.itemsArray().slice().sort((a, b) =>
         this.reportIsBefore(a, b) ? - 1 : 1