在你看来,你遇到过的最令人惊讶、最怪异、最奇怪或最“WTF”的语言特性是什么?

请每个回答只回答一个特征。


当前回答

不知道它是否可以被认为是一种语言特性,但是,在c++中,几乎任何与模板相关的编译器错误都会每天向世界各地的许多c++程序员交付相当数量的WTF:)

其他回答

这并不是说它被大量使用,而是c++的“返回对静态大小数组的引用”的语法很奇怪:

struct SuperFoo {
  int (&getFoo() const)[10] {
    static int foo[10];
    return foo;
  }
}

在上述情况下,Ofc方法可以声明为静态const

Python 2。X演示了一个糟糕的列表理解实现:

z = 4
s = [z*z for z in range(255)]
print z

这段代码返回254。列表推导式的变量与上定义的变量冲突。

Python 3。x已经处理了这个特性,但是闭包仍然对外部变量使用动态链接,并在函数式python编程器中引入了许多wtf

def mapper(x):
    return x*x
continuations = [lambda: mapper(x) for x in range(5)]
print( [c() for c in continuations])

此代码显然返回[16,16,16,16,16]。

Perl的许多内置变量:

$# — not a comment! $0, $$, and $? — just like the shell variables by the same name $ˋ, $&, and $' — weird matching variables $" and $, — weird variables for list- and output-field-separators $! — like errno as a number but strerror(errno) as a string $_ — the stealth variable, always used and never seen $#_ — index number of the last subroutine argument... maybe @_ — the (non)names of the current function... maybe $@ — the last-raised exception %:: — the symbol table $:, $^, $~, $-, and $= — something to do with output formats $. and $% — input line number, output page number $/ and $\ — input and output record separators $| — output buffering controller $[ — change your array base from 0-based to 1-based to 42-based: WHEEE! $} — nothing at all, oddly enough! $<, $>, $(, $) — real and effective UIDs and GIDs @ISA — names of current package’s direct superclasses $^T — script start-up time in epoch seconds $^O — current operating system name $^V — what version of Perl this is

还有很多这样的东西。点击这里阅读完整列表。

c++模板可以用来做一些奇怪的事情,最好的例子是“多维模拟字面量”,它使用模板来计算“绘制”形状的面积。下面的代码对于3x3矩形是有效的c++代码

#include"analogliterals.hpp"
using namespace analog_literals::symbols;

          unsigned int c = ( o-----o
                             |     !
                             !     !
                             !     !
                             o-----o ).area;

再举一个3D立方体的例子:

  assert( ( o-------------o
            |L             \
            | L             \
            |  L             \
            |   o-------------o
            |   !             !
            !   !             !
            o   |             !
             L  |             !
              L |             !
               L|             !
                o-------------o ).volume == ( o-------------o
                                              |             !
                                              !             !
                                              !             !
                                              o-------------o ).area * int(I-------------I) );

一个意想不到的特性是,在C、c#、Ruby等语言中,枚举定义列表和数组初始化列表中的末尾逗号。

string[] foods = { "tofu", "grits", "cabbage", }

public enum ArtPeriod {
  Modern,
  Romantic,
  Dada,
}