swift - 二元运算符 '+' 不能应用于两个 'int2' 操作数。需要使用 '&+'

Question

我正在尝试将一些代码从 Objective-C 转换为 Swift 并遇到这种情况:

import simd

let a = int2(1, 0)
let b = int2(0, 1)

print(a + b) // COMPILER FAILS
print(a &+ b) // SUCCESS

为什么要将完全可以理解的语法更改为这种神秘的符号？

Answer 1

摘自关于 Swift 2 的 Xcode 7 发行说明:

SIMD improvements: Integer vector types in the simd module now only support unchecked arithmetic with wraparound semantics using the &+, &-, and &* operators, in order to better support the machine model for vectors. The +, -, and * operators are unavailable on integer vectors, and Xcode automatically suggests replacing them with the wrapping operators.

(来自 https://developer.apple.com/library/ios/releasenotes/DeveloperTools/RN-Xcode/Chapters/xc7_release_notes.html)

不寻常的语法是专门用来明显地表明加法是用未经检查的算术完成的。