use a multiplication symbol when RHS is a negative number

The regex for the case when there's a real number on the LHS wasn't
checking if the RHS was a negative number, just if it started with a
digit.

Checking the string rendering of the RHS is a bit indirect, but it
articulates that you don't want a string of digits or + or - signs next
to each other.

Author: christianp

runtime/scripts/jme-display.js

@@ -426,8 +426,8 @@ var texOps = jme.display.texOps = {
                 // if we'd end up with two digits next to each other, but from different arguments, we need a times symbol
                 } else if(util.isInt(texArgs[i-1].charAt(texArgs[i-1].length-1)) && util.isInt(texArgs[i].charAt(0)) && !this.texifyWouldBracketOpArg(tree,i)) {
                     use_symbol = true;
-                //real number times something that doesn't start with a letter
-                } else if (jme.isType(left.tok,'number') && !isComplex(left.tok) && texArgs[i].match(/^[^0-9]/)) {
+                //real number times something that doesn't start with a digit or minus sign
+                } else if (jme.isType(left.tok,'number') && !isComplex(left.tok) && texArgs[i].match(/^[^\-+0-9]/)) {
                     use_symbol = false
                 //number times a power of i
                 } else if (jme.isOp(right.tok,'^') && jme.isType(right.args[0].tok,'number') && math.eq(right.args[0].tok.value,math.complex(0,1)) && jme.isType(left.tok,'number')) {

tests/jme-runtime.js

@@ -17862,8 +17862,8 @@ var texOps = jme.display.texOps = {
                 // if we'd end up with two digits next to each other, but from different arguments, we need a times symbol
                 } else if(util.isInt(texArgs[i-1].charAt(texArgs[i-1].length-1)) && util.isInt(texArgs[i].charAt(0)) && !this.texifyWouldBracketOpArg(tree,i)) {
                     use_symbol = true;
-                //real number times something that doesn't start with a letter
-                } else if (jme.isType(left.tok,'number') && !isComplex(left.tok) && texArgs[i].match(/^[^0-9]/)) {
+                //real number times something that doesn't start with a digit or minus sign
+                } else if (jme.isType(left.tok,'number') && !isComplex(left.tok) && texArgs[i].match(/^[^\-0-9]/)) {
                     use_symbol = false
                 //number times a power of i
                 } else if (jme.isOp(right.tok,'^') && jme.isType(right.args[0].tok,'number') && math.eq(right.args[0].tok.value,math.complex(0,1)) && jme.isType(left.tok,'number')) {

tests/jme/jme-tests.mjs

@@ -2334,6 +2334,12 @@ Numbas.queueScript('jme_tests',['qunit','jme','jme-rules','jme-display','jme-cal
         assert.equal(texify({tok:Numbas.jme.builtinScope.evaluate('matrix([1,2])')},{matrixcommas:false}),'\\left ( \\begin{matrix} 1 & 2 \\end{matrix} \\right )', 'one-row matrix has no commas with matrixcommas: false');
         assert.equal(texify({tok:Numbas.jme.builtinScope.evaluate('vector(1,2)')}, {rowvector: true}),'\\left ( 1 , 2 \\right )', 'row vector has commas');
         assert.equal(texify({tok:Numbas.jme.builtinScope.evaluate('vector(1,2)')}, {rowvector: true, matrixcommas: false}),'\\left ( 1 \\quad 2 \\right )', 'row vector has no commas with matrixcommas: false');
+
+        var tree = Numbas.jme.compile('a*b');
+        var scope = new Numbas.jme.Scope([Numbas.jme.builtinScope, {variables: {a:Numbas.jme.builtinScope.evaluate('-2'), b:Numbas.jme.builtinScope.evaluate('-3')}}]);
+        var t2 = Numbas.jme.substituteTree(tree,scope);
+        assert.equal(Numbas.jme.display.texify(t2,'',scope), '-2 \\times -3', 'multiplication symbol used when RHS is a negative number');
+        assert.equal(Numbas.jme.display.treeToJME(t2,'',scope), '-2(-3)', 'multiplication symbol used when RHS is a negative number');
     });
 
     QUnit.test('expression to LaTeX', function(assert) {

tests/numbas-runtime.js

@@ -17198,8 +17198,8 @@ var texOps = jme.display.texOps = {
                 // if we'd end up with two digits next to each other, but from different arguments, we need a times symbol
                 } else if(util.isInt(texArgs[i-1].charAt(texArgs[i-1].length-1)) && util.isInt(texArgs[i].charAt(0)) && !this.texifyWouldBracketOpArg(tree,i)) {
                     use_symbol = true;
-                //real number times something that doesn't start with a letter
-                } else if (jme.isType(left.tok,'number') && !isComplex(left.tok) && texArgs[i].match(/^[^0-9]/)) {
+                //real number times something that doesn't start with a digit or minus sign
+                } else if (jme.isType(left.tok,'number') && !isComplex(left.tok) && texArgs[i].match(/^[^\-0-9]/)) {
                     use_symbol = false
                 //number times a power of i
                 } else if (jme.isOp(right.tok,'^') && jme.isType(right.args[0].tok,'number') && math.eq(right.args[0].tok.value,math.complex(0,1)) && jme.isType(left.tok,'number')) {