如何在 Swift 中捕获算术溢出错误? [英] How does one trap arithmetic overflow errors in Swift?

问题描述

这个可能很容易.我们知道运算符 &+ 对整数进行模运算(环绕)，而运算符 + 会导致错误.

This one is probably easy. We know that the operator &+ does modular arithmetic on integers (wraps around), while the operator + causes an error.

$ swift
  1> var x: Int8 = 100
x: Int8 = 100
  2> x &+ x
$R0: Int8 = -56
  3> x + x
Execution interrupted. Enter Swift code to recover and continue.

这是什么错误?我无法抓住它，也无法将其转换为可选:

What kind of error is this? I can't catch it and I can't turn it in to an optional:

  4> do {try x + x} catch {print("got it")}
Execution interrupted. Enter Swift code to recover and continue.
  5> try? x + x
Execution interrupted. Enter Swift code to recover and continue.

我很确定这种错误与this Stack Overflow question中的错误相同(一个划分-by-zero) 但我不知道是否可以捕获这种错误.我错过了什么简单的事情?能不能被困?如果是，怎么办?

I'm pretty sure this kind of error is the same kind of error from this Stack Overflow question (a divide-by-zero) but I don't know if this kind of error can be trapped. What simple thing am I missing? Can it be trapped or not? If so, how?

推荐答案

区分异常和运行时错误.异常被抛出并且可以被捕获.运行时错误会使您的程序停止运行.添加和获取溢出是一个运行时错误，简单明了.没什么可抓的.

Distinguish between an exception and a runtime error. An exception is thrown and can be caught. A runtime error stops your program dead in its tracks. Adding and getting an overflow is a runtime error, plain and simple. There is nothing to catch.

像 &+ 这样的操作符的重点是它不会出错，也不会告诉你有问题.这就是重点.

The point of an operator like &+ is that it doesn't error and it doesn't tell you there was a problem. That is the whole point.

如果您认为自己可能会溢出，并且想知道是否会溢出，请使用诸如 addWithOverflow 之类的静态方法.它返回一个由结果和一个 Bool 组成的元组，说明是否存在溢出.

If you think you might overflow, and you want to know whether you did, use static methods like addWithOverflow. It returns a tuple consisting of the result and a Bool stating whether there was an overflow.

var x: Int8 = 100
let result = x &+ x // -56

x = 100
let result2 = Int8.addWithOverflow(x,x) // (-56, true)

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