evaluate_to_constant returns NaN for non-numeric, by default

Author: dqnykamp

build/math-expressions.js

@@ -153,7 +153,7 @@ function is_integer_ast(tree, assumptions, original_assumptions) {
 	return Number.isInteger(tree);
 
     // if can convert to constant, evaluate directly
-    var c = evaluate_to_constant(tree, false);
+    var c = evaluate_to_constant(tree, {remove_units_first: false, nan_for_non_numeric: false});
     if(c !== null) {
 	return Number.isInteger(c);
     }
@@ -436,7 +436,7 @@ function is_real_ast(tree, assumptions, original_assumptions) {
 	return Number.isFinite(tree);
 
     // if can convert to constant, evaluate directly
-    var c = evaluate_to_constant(tree, false);
+    var c = evaluate_to_constant(tree, {remove_units_first: false, nan_for_non_numeric: false});
 
     if(c !== null) {
 	if(typeof c === 'number') {
@@ -762,7 +762,7 @@ function is_complex_ast(tree, assumptions, original_assumptions) {
 	return Number.isFinite(tree);
 
     // if can convert to constant, evaluate directly
-    var c = evaluate_to_constant(tree, false);
+    var c = evaluate_to_constant(tree, {remove_units_first: false, nan_for_non_numeric: false});
     if(c !== null) {
 	if(typeof c === 'number') {
 	    return Number.isFinite(c);
@@ -1057,7 +1057,7 @@ function is_nonzero_ast(tree, assumptions, original_assumptions) {
     }
 
     // if can convert to constant, evaluate directly
-    var c = evaluate_to_constant(tree, false);
+    var c = evaluate_to_constant(tree, {remove_units_first: false, nan_for_non_numeric: false});
     if(c !== null) {
 	if(typeof c === 'number') {
 	    if(Number.isFinite(c))
@@ -1489,7 +1489,7 @@ function is_positive_ast(tree, assumptions, strict, original_assumptions) {
 	return is_real;
 
     // if can convert to constant, evaluate directly
-    var c = evaluate_to_constant(tree, false);
+    var c = evaluate_to_constant(tree, {remove_units_first: false, nan_for_non_numeric: false});
 
     if(c !== null) {
 	if(typeof c === 'number') {

build/math-expressions_umd.js

@@ -32,17 +32,20 @@ const evaluate = function (expr, bindings) {
 //     return parser.ast.to.finiteField( expr.tree, modulus )( bindings );
 // };
 
-const evaluate_to_constant = function (expr_or_tree, remove_units_first = true, scale_based_on_unit = true) {
+const evaluate_to_constant = function (expr_or_tree,
+  { remove_units_first = true, scale_based_on_unit = true, nan_for_non_numeric = true } = {}
+) {
   // evaluate to number by converting tree to number
   // and calling without arguments
 
-  // return null if couldn't evaluate to constant (e.g., contains a variable)
-  // otherwise returns constant
+  // return NaN (or null if nan_for_non_numeric is false) 
+  // if couldn't evaluate to constant (e.g., contains a variable)
+  // otherwise returns constant (which could be NaN for an expression like 0/0)
   // NOTE: constant could be a math.js complex number object
 
   var tree = get_tree(expr_or_tree);
 
-  if(remove_units_first) {
+  if (remove_units_first) {
     tree = remove_units(tree, scale_based_on_unit);
   }
 
@@ -56,14 +59,14 @@ const evaluate_to_constant = function (expr_or_tree, remove_units_first = true,
     } else if (tree === "i" && math.define_i) {
       return { re: 0, im: 1 };
     }
-    return null;
+    return nan_for_non_numeric ? NaN : null;
   }
 
   if (!Array.isArray(tree)) {
-    return null;
+    return nan_for_non_numeric ? NaN : null;
   }
 
-  var num = null;
+  var num = nan_for_non_numeric ? NaN : null;
   try {
     var the_f = f(tree);
     num = the_f();

lib/assumptions/element_of_sets.js

@@ -584,9 +584,9 @@ function evaluate_numbers_sub(tree, assumptions, max_digits, skip_ordering, eval
       return null;
     }
 
-    var c = evaluate_to_constant(tree, false);
+    var c = evaluate_to_constant(tree, {remove_units_first: false});
 
-    if (c !== null) {
+    if (!Number.isNaN(c)) {
       if (typeof c === 'number') {
         if (Number.isFinite(c)) {
           let n = simplify_number(c);
@@ -882,8 +882,8 @@ function collect_like_terms_factors(expr_or_tree, assumptions, max_digits) {
       return true;
     if (Array.isArray(s) && s[0] === '-' && (typeof s[1] === 'number'))
       return true;
-    let c = evaluate_to_constant(s, false);
-    if (typeof c === 'number' && Number.isFinite(c))
+    var c = evaluate_to_constant(s, {remove_units_first: false});
+    if (Number.isFinite(c))
       return true;
 
     return false;

lib/expression/evaluation.js

@@ -24,8 +24,8 @@ function expression_to_polynomial(expr_or_tree) {
     if(typeof tree === 'number')
 	return tree;
 
-    let c = evaluate_to_constant(tree, false);
-    if(c !== null && Number.isFinite(c)) {
+    var c = evaluate_to_constant(tree, {remove_units_first: false});
+    if(Number.isFinite(c)) {
 	return simplify.simplify(tree);
     }
 
@@ -80,10 +80,10 @@ function expression_to_polynomial(expr_or_tree) {
 	// if pow isn't a literal nonnegative integer
 	if((typeof pow !== 'number') || pow < 0 || !Number.isInteger(pow)) {
 
-	    let pow_num = evaluate_to_constant(pow, false);
+	    let pow_num = evaluate_to_constant(pow, {remove_units_first: false});
 
 	    // check if pow is a rational number with a small base
-	    if(pow_num !== null || Number.isFinite(pow_num)) {
+	    if(Number.isFinite(pow_num)) {
 		let pow_fraction = math.fraction(pow_num);
 		if(pow_fraction.d <= 100) {
 		    if(pow_fraction.s < 0)
@@ -117,9 +117,9 @@ function expression_to_polynomial(expr_or_tree) {
     else if(operator === '/') {
 	var denom = operands[1];
 
-	var denom_num = evaluate_to_constant(denom, false);
+	var denom_num = evaluate_to_constant(denom, {remove_units_first: false});
 
-	if(denom_num === null || !Number.isFinite(denom_num)) {
+	if(!Number.isFinite(denom_num)) {
 	    // return entire tree as polynomial variable
 	    return ['polynomial', tree, [[1, 1]]];
 	}

lib/expression/simplify.js

@@ -1,7 +1,7 @@
 {
   "name": "math-expressions",
   "description": "Perform basic equality testing and symbolic computations on mathematical expressions involving transcendental functions",
-  "version": "2.0.0-alpha59",
+  "version": "2.0.0-alpha60",
   "author": {
     "name": "Jim Fowler",
     "email": "[email protected]",

lib/polynomial/polynomial.js

@@ -276,8 +276,8 @@ describe("evaluate_to_constant", function () {
 
   });
 
-  it("with blanks gives null", function () {
-    expect(me.fromText("1+2+").evaluate_to_constant()).toEqual(null);
+  it("with blanks gives NaN", function () {
+    expect(me.fromText("1+2+").evaluate_to_constant()).toEqual(NaN);
   })
 
   it("multiple pluses and minus", function () {
@@ -298,19 +298,19 @@ describe("evaluate_to_constant", function () {
   })
 
   it("with units", function () {
-    expect(me.fromText("50%").evaluate_to_constant(false)).toEqual(null);
+    expect(me.fromText("50%").evaluate_to_constant({remove_units_first:false})).toEqual(NaN);
     expect(me.fromText("50%").evaluate_to_constant()).toEqual(0.5);
-    expect(me.fromText("50%").evaluate_to_constant(true, false)).toEqual(50);
+    expect(me.fromText("50%").evaluate_to_constant({scale_based_on_unit: false})).toEqual(50);
     expect(me.fromText("50%").remove_units().evaluate_to_constant()).toEqual(0.5);
     expect(me.fromText("50%").remove_units(false).evaluate_to_constant()).toEqual(50);
-    expect(me.fromText("$9.5").evaluate_to_constant(false)).toEqual(null);
+    expect(me.fromText("$9.5").evaluate_to_constant({remove_units_first:false})).toEqual(NaN);
     expect(me.fromText("$9.5").evaluate_to_constant()).toEqual(9.5);
-    expect(me.fromText("$9.5").evaluate_to_constant(true, false)).toEqual(9.5);
+    expect(me.fromText("$9.5").evaluate_to_constant({scale_based_on_unit: false})).toEqual(9.5);
     expect(me.fromText("$9.5").remove_units().evaluate_to_constant()).toEqual(9.5);
     expect(me.fromText("$9.5").remove_units(false).evaluate_to_constant()).toEqual(9.5);
-    expect(me.fromText("180deg").evaluate_to_constant(false)).toEqual(null);
+    expect(me.fromText("180deg").evaluate_to_constant({remove_units_first:false})).toEqual(NaN);
     expect(me.fromText("180deg").evaluate_to_constant()).toEqual(Math.PI);
-    expect(me.fromText("180deg").evaluate_to_constant(true, false)).toEqual(180);
+    expect(me.fromText("180deg").evaluate_to_constant({scale_based_on_unit: false})).toEqual(180);
     expect(me.fromText("180deg").remove_units().evaluate_to_constant()).toEqual(Math.PI);
     expect(me.fromText("180deg").remove_units(false).evaluate_to_constant()).toEqual(180);
   })