added "Find First" primitive to lists category

HISTORY.md

@@ -28,7 +28,7 @@
     * new "get graphic effect" reporter
     * new "get pen attribute" reporter
     * new "write" command in pen category (used to be "label" in tools)
-    * new "numbers", "is empty", "map","keep", "combine" and "for each" primitives in list category
+    * new "numbers", "is empty", "map","keep", "find", "combine" and "for each" primitives in list category
     * new JIT-compiler "blitz-HOF" primitives for "map", "keep" & "combine" via "compile"
     * new "for" loop and "if then else" reporter primitives in the Control category
     * added "neg", "lg" (log2) and "2^" selectors to monadic function reporter in Operators
@@ -80,6 +80,9 @@
     * German
     * French
 
+### 2019-05-29
+* Threads, Objects: added "Find First" primitive to lists category
+
 ### 2019-05-28
 * Maps: added various different tile hosts
 * added "set map style" command to maps library

snap.html

@@ -7,8 +7,8 @@
         <script type="text/javascript" src="src/morphic.js?version=2019-05-21"></script>
         <script type="text/javascript" src="src/widgets.js?version=2019-04-05"></script>
         <script type="text/javascript" src="src/blocks.js?version=2019-05-20"></script>
-        <script type="text/javascript" src="src/threads.js?version=2019-05-15"></script>
-        <script type="text/javascript" src="src/objects.js?version=2019-05-25"></script>
+        <script type="text/javascript" src="src/threads.js?version=2019-05-29"></script>
+        <script type="text/javascript" src="src/objects.js?version=2019-05-29"></script>
         <script type="text/javascript" src="src/gui.js?version=2019-05-09"></script>
         <script type="text/javascript" src="src/paint.js?version=2019-02-22"></script>
         <script type="text/javascript" src="src/lists.js?version=2019-04-27"></script>

src/objects.js

@@ -84,7 +84,7 @@ BlockEditorMorph, BlockDialogMorph, PrototypeHatBlockMorph, localize,
 TableMorph, TableFrameMorph, normalizeCanvas, BooleanSlotMorph, HandleMorph,
 AlignmentMorph, Process, XML_Element, VectorPaintEditorMorph, WorldMap*/
 
-modules.objects = '2019-May-24';
+modules.objects = '2019-May-29';
 
 var SpriteMorph;
 var StageMorph;
@@ -1312,6 +1312,11 @@ SpriteMorph.prototype.initBlocks = function () {
             category: 'lists',
             spec: '%blitz keep items such that %predRing from %l'
         },
+        reportFindFirst: {
+            type: 'reporter',
+            category: 'lists',
+            spec: 'find first item such that %predRing in %l'
+        },
         reportCombine: {
             type: 'reporter',
             category: 'lists',
@@ -1560,10 +1565,11 @@ SpriteMorph.prototype.blockAlternatives = {
     doShowVar: ['doHideVar'],
     doHideVar: ['doShowVar'],
 
-    // lists - blitz primitives
-    reportMap: ['reportKeep', 'reportCombine'],
-    reportKeep: ['reportMap', 'reportCombine'],
-    reportCombine: ['reportMap', 'reportKeep']
+    // lists - HOFs
+    reportMap: ['reportKeep', 'reportFindFirst', 'reportCombine'],
+    reportKeep: ['reportFindFirst', 'reportMap', 'reportCombine'],
+    reportCombine: ['reportMap', 'reportKeep', 'reportFindFirst'],
+    reportFindFirst: ['reportKeep', 'reportMap', 'reportCombine']
 };
 
 // SpriteMorph instance creation
@@ -2550,6 +2556,7 @@ SpriteMorph.prototype.blockTemplates = function (category) {
         blocks.push('-');
         blocks.push(block('reportMap'));
         blocks.push(block('reportKeep'));
+        blocks.push(block('reportFindFirst'));
         blocks.push(block('reportCombine'));
         blocks.push('-');
         blocks.push(block('doForEach'));
@@ -2737,6 +2744,7 @@ SpriteMorph.prototype.freshPalette = function (category) {
                         'doForEach',
                         'reportMap',
                         'reportKeep',
+                        'reportFindFirst',
                         'reportCombine',
                         'doAddToList',
                         'doDeleteFromList',
@@ -8289,6 +8297,7 @@ StageMorph.prototype.blockTemplates = function (category) {
         blocks.push('-');
         blocks.push(block('reportMap'));
         blocks.push(block('reportKeep'));
+        blocks.push(block('reportFindFirst'));
         blocks.push(block('reportCombine'));
         blocks.push('-');
         blocks.push(block('doForEach'));

src/threads.js

@@ -61,7 +61,7 @@ StageMorph, SpriteMorph, StagePrompterMorph, Note, modules, isString, copy,
 isNil, WatcherMorph, List, ListWatcherMorph, alert, console, TableMorph, Color,
 TableFrameMorph, ColorSlotMorph, isSnapObject, Map, newCanvas, Symbol*/
 
-modules.threads = '2019-May-15';
+modules.threads = '2019-May-29';
 
 var ThreadManager;
 var Process;
@@ -2339,6 +2339,61 @@ Process.prototype.reportKeep = function (predicate, list) {
     this.evaluate(predicate, new List([next]));
 };
 
+Process.prototype.reportFindFirst = function (predicate, list) {
+    // Find - answer the first item of the list for which
+    // the predicate evaluates TRUE.
+    // Distinguish between linked and arrayed lists.
+
+    var next;
+    this.assertType(list, 'list');
+    if (list.isLinked) {
+        if (this.context.accumulator === null) {
+            this.context.accumulator = {
+                source : list,
+                remaining : list.length()
+            };
+        } else if (this.context.inputs.length > 2) {
+            if (this.context.inputs.pop() === true) {
+                this.returnValueToParentContext(
+                    this.context.accumulator.source.at(1)
+                );
+                return;
+            }
+            this.context.accumulator.remaining -= 1;
+            this.context.accumulator.source =
+                this.context.accumulator.source.cdr();
+        }
+        if (this.context.accumulator.remaining === 0) {
+            this.returnValueToParentContext(false);
+            return;
+        }
+        next = this.context.accumulator.source.at(1);
+    } else { // arrayed
+        if (this.context.accumulator === null) {
+            this.context.accumulator = {
+                idx : 0,
+                current : null
+            };
+        } else if (this.context.inputs.length > 2) {
+            if (this.context.inputs.pop() === true) {
+                this.returnValueToParentContext(
+                    this.context.accumulator.current
+                );
+                return;
+            }
+        }
+        if (this.context.accumulator.idx === list.length()) {
+            this.returnValueToParentContext(false);
+            return;
+        }
+        this.context.accumulator.idx += 1;
+        next = list.at(this.context.accumulator.idx);
+        this.context.accumulator.current = next;
+    }
+    this.pushContext();
+    this.evaluate(predicate, new List([next]));
+};
+
 Process.prototype.reportCombine = function (reporter, list) {
     // Fold - answer an aggregation of all list items from "left to right"
     // Distinguish between linked and arrayed lists.