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商上的加速C ++

[英]Accelerated C++ on quotients

原文 2015-05-23 09:55:20 6 1 c++/ division/ accelerated-c++

I am reading the book "Accelerated C++". 我正在读《加速C ++》这本书。 In the details of chapter 2, a description of division between two numbers and extracting their quotient is provided: 在第2章的详细信息中，提供了两个数字之间的除法并提取其商的描述：

x / y x / y

Quotient of x and y . x和y的商。 If both operands are integers, the implementation chooses whether to round toward zero or - 8 如果两个操作数都是整数，则实现选择是四舍五入为零还是-8

I don't understand this one. 我不明白这一点。 What does "round toward [...] - 8" mean? “朝[...]-8进位”是什么意思？ What implementations use that and why? 哪些实现使用它，为什么？

Well I tried searching for that but didn't find anything. 好吧，我尝试搜索，但是什么也没找到。

1 个解决方案

The book probably means round towards negative infinity , ie -∞: 这本书可能意味着朝负无穷大方向舍入，即-∞：

Directed roundings 有向四舍五入

Round toward 0 – directed rounding towards zero (also known as truncation). 向0舍入–向0定向舍入（也称为截断）。
Round toward +∞ – directed rounding towards positive infinity (also known as rounding up or ceiling). 向+∞舍入–朝正无穷大方向舍入（也称为向上舍入或上限）。
Round toward −∞ – directed rounding towards negative infinity (also known as rounding down or floor). 向-∞取整-朝负无穷大方向定向（也称为向下取整或向下取整）。

Either there was a typesetting error, or you are not seeing it correctly. 可能是排版错误，或者您没有正确看到它。