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LibJS: Add a modulo() function to represent the "x modulo y" notation

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This *not* being the same as C++ "%" in all cases is a massive footgun,
and hopefully one I came across for the last time.
This commit is contained in:
Linus Groh 2021-11-07 20:48:38 +00:00
parent e93ce1ff69
commit 3d84fb64c3
1 changed files with 14 additions and 0 deletions
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14
Userland/Libraries/LibJS/Runtime/AbstractOperations.h
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@ -76,4 +76,18 @@ ThrowCompletionOr<T*> ordinary_create_from_constructor(GlobalObject& global_obje
return global_object.heap().allocate<T>(global_object, forward<Args>(args)..., *prototype); return global_object.heap().allocate<T>(global_object, forward<Args>(args)..., *prototype);
} }
// x modulo y, https://tc39.es/ecma262/#eqn-modulo
template<typename T>
T modulo(T x, T y)
{
// The notation “x modulo y” (y must be finite and non-zero) computes a value k of the same sign as y (or zero) such that abs(k) < abs(y) and x - k = q × y for some integer q.
VERIFY(y != 0);
if constexpr (IsFloatingPoint<T>) {
VERIFY(isfinite(y));
return fmod(fmod(x, y) + y, y);
} else {
return ((x % y) + y) % y;
}
}
} }