constexpr exp，日志，战俘 [英] constexpr exp, log, pow

问题描述

我想以可移植的方式使用标准<cmath>函数的constexpr版本，例如exp，log，pow.我目前有一个非便携式解决方案 g++将这些功能视为constexpr-C ++的不兼容扩展，但是我担心可移植性和面向未来的发展(我想也许有一天可以从g++中删除此扩展).

I'd like to use constexpr versions of standard <cmath> functions like exp, log, pow in a portable way. I currently have a non-portable solution g++ treats these functions as constexpr - a non-compliant extension of C++, but I am concerned about portability and future-proofing (I imagine that this extension might one day be removed from g++).

我对这些函数的constexpr版本感兴趣，而不是模板元程序-我希望在编译时和运行时都可以使用相同的功能.我不需要C兼容性，但是我需要快速实现-像Taylor Series扩展这样的幼稚实现会太慢.

I am interested in constexpr versions of these functions, not template metaprograms - I want the same functionality to be available both at compile time and runtime. I do not need C compatibility, but I do need fast implementations - naive implementations such as Taylor Series expansions would be too slow.

如何实现这些功能?我对exp，log和pow

我从研究中学到的一些切线相关的东西

• 这些函数的标准兼容版本在技术上不是constexpr，因为它们必须具有副作用(例如，设置errno)才能保持C兼容性
• 在C ++ 11中，允许实现使这些功能成为constexpr，但是从C ++ 14开始，这被禁止(根据

• The standard-compliant versions of these functions aren't technically constexpr because they must have side-effects (e.g. setting errno) to maintain C compatibility
• In C++11, an implementation was allowed to make these functions constexpr, but as of C++14, this is prohibited (per the first answer to this question and the answer to this question). This is part of the reason that I am concerned that the functions may not be constexpr in future versions of g++
• g++'s implementation of each math function foo just calls a built-in function __builtin_foo, which is treated as constexpr. I could perhaps start calling the __builtin_foo functions rather than the foo functions - these might remain constexpr in future versions of g++ even if the corresponding foo functions are made compliant - but this only helps with future-proofing, not with portability.

推荐答案

您曾经看过发芽的实现?

Sprout是仅标头的库，它提供基于C ++ 11/14 constexpr的容器，算法，随机数，解析，光线跟踪，合成器等.

Sprout is header-only library that provide C++11/14 constexpr based Containers, Algorithms, Random numbers, Parsing, Ray tracing, Synthesizer, and others.

https://github.com/bolero-MURAKAMI/Sprout/树/主/新芽/数学

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