Merge pull request #275 from desmosinc/fix-binom

Fix \binom and \choose
desmosinc · Feb 29, 2024 · 43f0c60 · 43f0c60
2 parents b47f030 + e35463c
commit 43f0c60
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Showing 4 changed files with 151 additions and 2 deletions.
diff --git a/src/commands/math/commands.ts b/src/commands/math/commands.ts
@@ -939,7 +939,12 @@ var LiveFraction =
         if (!this.replacedFragment) {
           var leftward = cursor[L];
 
-          if (!cursor.options.typingSlashCreatesNewFraction) {
+          const dontScan =
+            cursor.options.typingSlashCreatesNewFraction &&
+            this instanceof Fraction;
+
+          if (!dontScan) {
+            // The user is typing "/" or "over" or "choose". Scan left to get content inside it.
             while (
               leftward &&
               !(
@@ -956,6 +961,8 @@ var LiveFraction =
             leftward instanceof SummationNotation &&
             leftward[R] instanceof SupSub
           ) {
+            // The previous step scanned too far. `\sum_1^5` looks like [SummationNotation,SupSub],
+            // so scan back right
             leftward = leftward[R] as MQNode;
             let leftwardR = leftward[R];
             if (
@@ -965,6 +972,9 @@ var LiveFraction =
               leftward = leftward[R];
           }
 
+          // `leftward` is the first node (from-right-to-left) that is broken on, so
+          // `leftwardR` is the last node (from right-to-left) that should be included in the
+          // top of the Fraction or Binomial.
           if (leftward !== cursor[L] && !cursor.isTooDeep(1)) {
             let leftwardR = (leftward as MQNode)[R] as MQNode;
             let cursorL = cursor[L] as MQNode;
@@ -1677,13 +1687,23 @@ class Binomial extends DelimsNode {
   textTemplate = ['choose(', ',', ')'];
   mathspeakTemplate = ['StartBinomial,', 'Choose', ', EndBinomial'];
   ariaLabel = 'binomial';
+
+  finalizeTree() {
+    const endsL = this.getEnd(L);
+    const endsR = this.getEnd(R);
+    this.upInto = endsR.upOutOf = endsL;
+    this.downInto = endsL.downOutOf = endsR;
+    // https://math.stackexchange.com/a/1617456 cites Knuth as the source of 'upper index' and 'lower index'
+    endsL.ariaLabel = 'upper index';
+    endsR.ariaLabel = 'lower index';
+  }
 }
 
 LatexCmds.binom = LatexCmds.binomial = Binomial;
 
 LatexCmds.choose = class extends Binomial {
   createLeftOf(cursor: Cursor) {
-    LiveFraction.prototype.createLeftOf(cursor);
+    LiveFraction.prototype.createLeftOf.call(this, cursor);
   }
 };
 

diff --git a/test/unit/aria.test.js b/test/unit/aria.test.js
@@ -140,6 +140,41 @@ suite('aria', function () {
     mathField.latex('');
   });
 
+  test('typing and backspacing a binomial', function () {
+    mathField.typedText('1');
+    assertAriaEqual('1');
+    mathField.cmd('\\choose');
+    // Matching behavior of "over", we don't get "choose" as the ARIA here.
+    mathField.typedText('2');
+    assertAriaEqual('2');
+
+    mathField.keystroke('Tab');
+    assertAriaEqual('after StartBinomial, 1 Choose 2 , EndBinomial');
+
+    mathField.keystroke('Backspace');
+    assertAriaEqual('end of lower index 2');
+    mathField.keystroke('Backspace');
+    assertAriaEqual('2');
+    mathField.keystroke('Backspace');
+    assertAriaEqual('Choose');
+    mathField.keystroke('Backspace');
+    assertAriaEqual('1');
+  });
+
+  test('navigating a binomial', function () {
+    mathField.typedText('1');
+    assertAriaEqual('1');
+    mathField.cmd('\\choose');
+    // Matching behavior of "over", we don't get "choose" as the ARIA here.
+    mathField.typedText('2');
+    assertAriaEqual('2');
+    mathField.keystroke('Up');
+    assertAriaEqual('upper index 1');
+    mathField.keystroke('Down');
+    assertAriaEqual('lower index 2');
+    mathField.latex('');
+  });
+
   test('typing and backspacing through parenthesies', function () {
     mathField.typedText('(');
     assertAriaEqual('left parenthesis');

diff --git a/test/unit/typing.test.js b/test/unit/typing.test.js
@@ -63,6 +63,24 @@ suite('typing with auto-replaces', function () {
     });
   });
 
+  suite('Choose', function () {
+    test('full MathQuill', function () {
+      mq.typedText('1').cmd('\\choose').typedText('2').keystroke('Tab');
+      mq.typedText('+sinx').cmd('\\choose');
+      assertLatex('\\binom{1}{2}+\\binom{\\sin x}{ }');
+      mq.latex('').typedText('1+').cmd('\\choose').typedText('2');
+      assertLatex('1+\\binom{2}{ }');
+      mq.latex('').typedText('1 2').cmd('\\choose').typedText('3');
+      assertLatex('1\\ \\binom{2}{3}');
+    });
+
+    test('mathquill-basic', function () {
+      var mq_basic = MQBasic.MathField($('<span></span>').appendTo('#mock')[0]);
+      mq_basic.typedText('1').cmd('\\choose').typedText('2');
+      assert.equal(mq_basic.latex(), '\\binom{1}{2}');
+    });
+  });
+
   suite('EquivalentMinus', function () {
     test('different minus symbols', function () {
       //these 4 are all different characters (!!)
@@ -1201,6 +1219,11 @@ suite('typing with auto-replaces', function () {
       mq.typedText('1/');
       assertLatex('1\\frac{ }{ }');
     });
+
+    test("typing slash creates new fraction doesn't affect choose", function () {
+      mq.typedText('1').cmd('\\choose');
+      assertLatex('\\binom{1}{ }');
+    });
   });
 
   suite('autoCommands', function () {

diff --git a/test/unit/updown.test.js b/test/unit/updown.test.js
@@ -186,6 +186,77 @@ suite('up/down', function () {
     );
   });
 
+  test('up/down into and within binomial', function () {
+    controller.renderLatexMath('\\binom{12}{34}');
+    var binom = rootBlock.ends[L],
+      numer = binom.ends[L],
+      denom = binom.ends[R];
+    assert.equal(binom.latex(), '\\binom{12}{34}', 'binomial is in root block');
+    assert.equal(
+      binom,
+      rootBlock.ends[R],
+      'binomial is sole child of root block'
+    );
+    assert.equal(
+      numer.latex(),
+      '12',
+      'numerator is left end child of binomial'
+    );
+    assert.equal(
+      denom.latex(),
+      '34',
+      'denominator is right end child of binomial'
+    );
+
+    mq.keystroke('Up');
+    assert.equal(cursor.parent, numer, 'cursor up goes into numerator');
+    assert.equal(
+      cursor[R],
+      0,
+      'cursor up from right of binomial inserts at right end of numerator'
+    );
+
+    mq.keystroke('Down');
+    assert.equal(cursor.parent, denom, 'cursor down goes into denominator');
+    assert.equal(
+      cursor[R],
+      0,
+      'cursor down from numerator inserts at right end of denominator'
+    );
+
+    mq.keystroke('Up');
+    assert.equal(cursor.parent, numer, 'cursor up goes into numerator');
+    assert.equal(
+      cursor[R],
+      0,
+      'cursor up from denominator inserts at right end of numerator'
+    );
+
+    mq.keystroke('Left Left Left');
+    assert.equal(cursor.parent, rootBlock, 'cursor outside binomial');
+    assert.equal(cursor[R], binom, 'cursor before binomial');
+
+    mq.keystroke('Up');
+    assert.equal(cursor.parent, numer, 'cursor up goes into numerator');
+    assert.equal(
+      cursor[L],
+      0,
+      'cursor up from left of binomial inserts at left end of numerator'
+    );
+
+    mq.keystroke('Left');
+    assert.equal(cursor.parent, rootBlock, 'cursor outside binomial');
+    assert.equal(cursor[R], binom, 'cursor before binomial');
+
+    mq.keystroke('Down');
+    assert.equal(cursor.parent, denom, 'cursor down goes into denominator');
+    assert.equal(
+      cursor[L],
+      0,
+      'cursor down from left of binomial inserts at left end of denominator'
+    );
+  });
+
   test('nested subscripts and fractions', function () {
     controller.renderLatexMath(
       '\\frac{d}{dx_{\\frac{24}{36}0}}\\sqrt{x}=x^{\\frac{1}{2}}'