diff --git a/blocks.js b/blocks.js
index 3f644e79..7526a15d 100644
--- a/blocks.js
+++ b/blocks.js
@@ -149,7 +149,7 @@ isSnapObject, copy, PushButtonMorph, SpriteIconMorph, Process, AlignmentMorph*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.blocks = '2016-December-12';
+modules.blocks = '2016-December-19';
 
 var SyntaxElementMorph;
 var BlockMorph;
@@ -12330,7 +12330,8 @@ CommentMorph.prototype.fixLayout = function () {
 
 CommentMorph.prototype.userMenu = function () {
     var menu = new MenuMorph(this),
-        myself = this;
+        myself = this,
+        block = this.blockify();
 
     menu.addItem(
         "duplicate",
@@ -12353,6 +12354,24 @@ CommentMorph.prototype.userMenu = function () {
         },
         'open a new window\nwith a picture of this comment'
     );
+    if (block) {
+        menu.addLine();
+        menu.addItem(
+            block,
+            function () {
+                var world = myself.world(),
+                    ide = myself.parentThatIsA(IDE_Morph);
+                block.pickUp(world);
+                if (ide) {
+                    world.hand.grabOrigin = {
+                        origin: ide.palette,
+                        position: ide.palette.center()
+                    };
+                }
+            },
+            'blockify this expression'
+        );
+    }
     return menu;
 };
 
@@ -12489,6 +12508,125 @@ CommentMorph.prototype.stackHeight = function () {
     return this.height();
 };
 
+// CommentMorph parsing simple arithmetic expressions to reporters
+
+CommentMorph.prototype.blockify = function () {
+    // highly experimental Christmas Easter Egg 2016 :-)
+    var ast;
+
+    function parseInfix(expression, operator, already) {
+        // very basic binary infix parser for arithmetic expressions
+        // with strict left-to-right operator precedence (like in Smalltalk)
+        // which can be overriden by - nested - parentheses.
+        // assumes well-formed expressions, no graceful error handling yet.
+
+        var inputs = ['', ''],
+            idx = 0,
+            ch;
+
+        function format(value) {
+            return value instanceof Array || isNaN(+value) ? value : +value;
+        }
+
+        function nested() {
+            var level = 1,
+                expr = '';
+            while (idx < expression.length) {
+                ch = expression[idx];
+                idx += 1;
+                switch (ch) {
+                case '(':
+                    level += 1;
+                    break;
+                case ')':
+                    level -= 1;
+                    if (!level) {
+                        return expr;
+                    }
+                    break;
+                }
+                expr += ch;
+            }
+        }
+
+        while (idx < expression.length) {
+            ch = expression[idx];
+            idx += 1;
+            switch (ch) {
+            case ' ':
+                break;
+            case '(':
+                inputs[operator ? 1 : 0] = parseInfix(nested());
+                break;
+            case '-':
+            case '+':
+            case '*':
+            case '/':
+                if (!operator && !inputs[0].length) {
+                    inputs[0] += ch;
+                } else if (operator) {
+                    return parseInfix(
+                        expression.slice(idx),
+                        ch,
+                        [operator, already, format(inputs[1])]
+                    );
+                } else {
+                    operator = ch;
+                    already = format(inputs[0]);
+                }
+                break;
+            default:
+                inputs[operator ? 1 : 0] += ch;
+            }
+        }
+        if (operator) {
+            return [operator, already, format(inputs[1])];
+        }
+        return format(inputs[0]);
+    }
+
+    function blockFromAST(ast) {
+        var block, selectors, i, inps;
+        selectors = {
+            '+': 'reportSum',
+            '-': 'reportDifference',
+            '*': 'reportProduct',
+            '/': 'reportQuotient'
+        };
+        block = SpriteMorph.prototype.blockForSelector(selectors[ast[0]], true);
+        block.isDraggable = true;
+        inps = block.inputs();
+        for (i = 1; i < 3; i += 1) {
+            if (ast[i] instanceof Array) {
+                block.silentReplaceInput(inps[i - 1], blockFromAST(ast[i]));
+            } else if (isString(ast[i])) {
+                block.silentReplaceInput(
+                    inps[i - 1],
+                    SpriteMorph.prototype.variableBlock(ast[i])
+                );
+            } else { // number
+                inps[i - 1].setContents(ast[i]);
+            }
+        }
+        block.fixLayout();
+        block.fixBlockColor(null, true);
+        return block;
+    }
+
+    if (this.contents.text.length > 100) {return null; }
+    if (Process.prototype.isCatchingErrors) {
+        try {
+            ast = parseInfix(this.contents.text);
+            return ast instanceof Array ? blockFromAST(ast) : null;
+        } catch (error) {
+            return null;
+        }
+    } else {
+        ast = parseInfix(this.contents.text);
+        return ast instanceof Array ? blockFromAST(ast) : null;
+    }
+};
+
 // ScriptFocusMorph //////////////////////////////////////////////////////////
 
 /*
diff --git a/history.txt b/history.txt
index f0e9c1b3..8b8155a1 100755
--- a/history.txt
+++ b/history.txt
@@ -3196,6 +3196,7 @@ http://snap.berkeley.edu/run#cloud:Username=jens&ProjectName=rotation
 161219
 ------
 * GUI: new url-switch: &noExitWarning
+* Blocks: highly experimental infix-expression-to-reporter parser
 
 
 == v4.10 === (in development)
@@ -3210,6 +3211,7 @@ Features:
 * new url option switch: &noExitWarning
 * svg support for images from the web (svg files have been supported for a long time)
 * use media dialog for browsing and importing sounds
+* highly experimental infix-expression-to-reporter parser
 
 Fixes:
 * Music (play note) to work again in new and recent browser versions (Chrome 55)