setw()不会影响读取整数字段 [英] setw() does not affect reading integer fields

问题描述

我写了这样的代码:

int d{ 0 };
cin >> setw(2) >> d;

但是看来 setw()对读取整数没有影响.如果是这样，我们如何使用 istream 来实现 scanf()的％2d 行为?

But it seems setw() has no effect on reading integers. If so, how we could implement behaviour of %2d of scanf() with istream?

推荐答案

setw()不是设计的，不能用于整数类型.

setw() is not designed to be used with integral types.

它会做什么?提取整数的最后两位十进制数字?如果您将 std :: hex 放入流中，将会发生什么?

What would it do? Extract the last two decimal digits of the integer? What would happen if you had put std::hex into the stream?

最好的方法是先读取数字，然后自己处理.例如，如果要提取最低有效两位数，请随后使用 d％100 ；否则，请使用.对负数进行额外的修正.

The best approach is to read the number then deal with it yourself. For example, if you want to extract the least significant two digits, use d % 100 subsequently; making an extra correction for negative numbers.

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