fix: cleanup

Author: arnog

src/compute-engine/numerics/rationals.ts

@@ -96,7 +96,7 @@ export function add(lhs: Rational, rhs: Rational): Rational {
   if (n <= 9007199254740991 && n >= -9007199254740991 && d <= 9007199254740991)
     return [n, d];
 
-  if (!Number.isFinite(n) || !Number.isFinite(d)) return [n, d];
+  if (!Number.isFinite(n) || !Number.isFinite(d)) return [NaN, 1];
 
   return [
     BigInt(rhsNum[1]) * BigInt(lhs[0]) + BigInt(rhsNum[0]) * BigInt(lhs[1]),
@@ -115,7 +115,7 @@ export function mul(lhs: Rational, rhs: Rational): Rational {
     )
       return [n, d];
 
-    if (!Number.isFinite(n) || !Number.isFinite(d)) return [n, d];
+    if (!Number.isFinite(n) || !Number.isFinite(d)) return [NaN, 1];
 
     return [BigInt(lhs[0]) * BigInt(rhs[0]), BigInt(lhs[1]) * BigInt(rhs[1])];
   }

test/compute-engine/arithmetic.test.ts

@@ -892,6 +892,27 @@ describe('SUM', () => {
     ).toMatchInlineSnapshot(`25`);
   });
 
+  // Regression test for #287: product of Choose values losing precision
+  it('should compute product of large Choose values exactly', () => {
+    // Choose(35,7)*Choose(28,7)*Choose(21,7)*Choose(14,7)*Choose(7,7) = 35!/(7!)^5
+    const expr1 = ce.box([
+      'Multiply',
+      ['Binomial', 35, 7],
+      ['Binomial', 28, 7],
+      ['Binomial', 21, 7],
+      ['Binomial', 14, 7],
+      ['Binomial', 7, 7],
+    ]);
+    const expr2 = ce.box([
+      'Divide',
+      ['Factorial', 35],
+      ['Power', ['Factorial', 7], 5],
+    ]);
+    expect(expr1.evaluate().sub(expr2.evaluate()).evaluate().toString()).toBe(
+      '0'
+    );
+  });
+
   // Sum of binomial coefficients
   it('should simplify sum of binomial coefficients', () => {
     expect(