Swift Double.remainder(dividingBy :) returning negative value

Question

let num = 32.0
Double(num).remainder(dividingBy: 12.0)

我得到 -4？..而不是 8.0...它是从 8.0 中减去 12.0

我该如何解决这个问题？

Answer 1

请阅读 documentation小心:

For two finite values x and y, the remainder r of dividing x by y satisfies x == y * q + r, where q is the integer nearest to x / y. If x / y is exactly halfway between two integers, q is chosen to be even. Note that q is not x / y computed in floating-point arithmetic, and that q may not be representable in any available integer type.

(强调我的)

您想使用 truncatingRemainder(dividingBy:)相反:

let num = 32.0
let value = Double(num)
    .truncatingRemainder(dividingBy: 12)
print(value) // 8