c ++ boost lambda库

问题描述

解决方案

保留在C ++语言的边界之内和库，我建议先习惯使用STL算法函数模板进行编程，因为boost :: lambda最常见的用法是用内联表达式替换函子类。

库文档本身为您提供了一个前台示例：

  for_each a.begin（），a.end（），std :: cout<<<<<<<'';; 
  

其中 std :: cout<< _1<< ''产生一个函数对象，当被调用时，它的第一个参数写入 cout 流中。这是你可以用一个自定义函子类来做的事情， std :: ostream_iterator 或者一个显式循环，但是boost :: lambda可以简洁并且可能很清晰 - 至少如果你已经习惯了函数式编程概念。当你（使用STL）时，你会发现你对boost :: bind和boost :: lambda感兴趣。它很适合用于以下方面：

  std :: sort（c.begin（），c.end（）， bind（& Foo :: x，_1）< bind（& Foo :: x，_2））; 
  

在你达到那一点之前，不要太多。因此，使用STL算法，编写自己的函数，然后使用boost :: lambda将它们转换为内联表达式。

从专业的角度来看，我相信开始的最佳方法使用boost :: lambda来获取boost :: bind的理解和接受。在boost :: bind表达式中占位符的使用与裸boost :: lambda占位符相比看起来更不可思议，并且在代码审阅期间更容易被接受。超越基本的boost :: lambda使用很可能会让你的同事感到悲伤，除非你是在一个流血的C ++商店。

尽量不要过分 - -loop 真的是正确的解决方案。

What might be the best way to start programming using boost lambda libraries.

解决方案

Remaining within the boundaries of the C++ language and libraries, I would suggest first getting used to programming using STL algorithm function templates, as one the most common use you will have for boost::lambda is to replace functor classes with inlined expressions inlined.

The library documentation itself gives you an up-front example of what it is there for:

for_each(a.begin(), a.end(), std::cout << _1 << ' ');

where std::cout << _1 << ' ' produces a function object that, when called, writes its first argument to the cout stream. This is something you could do with a custom functor class, std::ostream_iterator or an explicit loop, but boost::lambda wins in conciseness and probably clarity -- at least if you are used to the functional programming concepts.

When you (over-)use the STL, you find yourself gravitating towards boost::bind and boost::lambda. It comes in really handy for things like:

std::sort( c.begin(), c.end(), bind(&Foo::x, _1) < bind(&Foo::x, _2) );

Before you get to that point, not so much. So use STL algorithms, write your own functors and then translate them into inline expressions using boost::lambda.

From a professional standpoint, I believe the best way to get started with boost::lambda is to get usage of boost::bind understood and accepted. Use of placeholders in a boost::bind expression looks much less magical than "naked" boost::lambda placeholders and finds easier acceptance during code reviews. Going beyond basic boost::lambda use is quite likely to get you grief from your coworkers unless you are in a bleeding-edge C++ shop.

Try not to go overboard - there are times when and places where a for-loop really is the right solution.

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