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LibJS: Add support for floating point modulous

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This change implements floating point mod based on the algorithm
used in LibM's fmod() implementation. To avoid taking a dependency
on LibM from LibJS I reimplemented the formula in LibJS.

I've incuded some of the example MDM test cases as well.
This surfaced and issue handling NaN which I've fixed as well.
This commit is contained in:
Brian Gianforcaro 2020-04-05 01:32:04 -07:00 • committed by Andreas Kling
parent 41bfff1abe
commit b8cef3a2d3
Notes: sideshowbarker 2024-07-19 07:54:36 +09:00
2 changed files with 22 additions and 2 deletions
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10
Libraries/LibJS/Runtime/Value.cpp
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@ -258,8 +258,14 @@ Value div(Value lhs, Value rhs)
Value mod(Value lhs, Value rhs)
{
// FIXME: It seems like JavaScript should allow modulo for doubles as well(?)
return Value(lhs.to_i32() % rhs.to_i32());
if (lhs.to_number().is_nan() || rhs.to_number().is_nan())
return js_nan();
double index = lhs.to_number().as_double();
double period = rhs.to_number().as_double();
double trunc = (double)(i32) (index / period);
return Value(index - trunc * period);
}
Value typed_eq(Value lhs, Value rhs)

14
Libraries/LibJS/Tests/modulo-basic.js
View file

@ -2,6 +2,20 @@ function assert(x) { if (!x) throw 1; }
try {
assert(10 % 3 === 1);
assert(10.5 % 2.5 === 0.5);
assert(-0.99 % 0.99 === -0);
// Examples form MDN:
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators
assert(12 % 5 === 2);
assert(-1 % 2 === -1);
assert(1 % -2 === 1);
assert(isNaN(NaN % 2);
assert(1 % 2 === 1);
assert(2 % 3 === 2);
assert(-4 % 2 === -0);
assert(5.5 % 2 === 1.5);
console.log("PASS");
} catch (e) {
console.log("FAIL: " + e);