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LibJS: Add spec comments and check for edge cases in Math.log

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davidot 2022-11-28 12:05:01 +01:00 committed by Andreas Kling
parent d4e5644df8
commit 4813385c9a
Notes: sideshowbarker 2024-07-17 05:18:58 +09:00 
Author: https://github.com/davidot
Commit: https://github.com/SerenityOS/serenity/commit/4813385c9a
Pull-request: https://github.com/SerenityOS/serenity/pull/16234
2 changed files with 23 additions and 3 deletions
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23
Userland/Libraries/LibJS/Runtime/MathObject.cpp
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@ -522,10 +522,27 @@ JS_DEFINE_NATIVE_FUNCTION(MathObject::imul)
// 21.3.2.20 Math.log ( x ), https://tc39.es/ecma262/#sec-math.log
JS_DEFINE_NATIVE_FUNCTION(MathObject::log)
{
auto value = TRY(vm.argument(0).to_number(vm)).as_double();
if (value < 0)
// 1. Let n be ? ToNumber(x).
auto number = TRY(vm.argument(0).to_number(vm));
// 2. If n is NaN or n is +∞𝔽, return n.
if (number.is_nan() || number.is_positive_infinity())
return number;
// 3. If n is 1𝔽, return +0𝔽.
if (number.as_double() == 1.)
return Value(0);
// 4. If n is +0𝔽 or n is -0𝔽, return -∞𝔽.
if (number.is_positive_zero() || number.is_negative_zero())
return js_negative_infinity();
// 5. If n < -0𝔽, return NaN.
if (number.as_double() < -0.)
return js_nan();
return Value(::log(value));
// 6. Return an implementation-approximated Number value representing the result of the natural logarithm of ℝ(n).
return Value(::log(number.as_double()));
}
// 21.3.2.23 Math.log2 ( x ), https://tc39.es/ecma262/#sec-math.log2

3
Userland/Libraries/LibJS/Tests/builtins/Math/Math.log.js
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@ -5,4 +5,7 @@ test("basic functionality", () => {
expect(Math.log(0)).toBe(-Infinity);
expect(Math.log(1)).toBe(0);
expect(Math.log(10)).toBeCloseTo(2.302585092994046);
expect(Math.log(NaN)).toBe(NaN);
expect(Math.log(Number.POSITIVE_INFINITY)).toBe(Number.POSITIVE_INFINITY);
expect(Math.log(-0.0)).toBe(Number.NEGATIVE_INFINITY);
});