的过程。Windows平台返回"win32"。在Windows上，用户的主目录可能是C:\Users[USERNAME]或C:\Documents and Settings[USERNAME]，这取决于正在使用的Windows版本。在Unix上，这不是问题。

javascript中是否有类似于Python的zip函数?也就是说，给定多个相等长度的数组，创建一个由对组成的数组。

例如，如果我有三个这样的数组:

var array1 = [1, 2, 3];
var array2 = ['a','b','c'];
var array3 = [4, 5, 6];

输出数组应该是:

var outputArray = [[1,'a',4], [2,'b',5], [3,'c',6]]

尽管我很喜欢C和c++，但我还是忍不住对空结尾字符串的选择抓耳挠脑:

Length prefixed (i.e. Pascal) strings existed before C Length prefixed strings make several algorithms faster by allowing constant time length lookup. Length prefixed strings make it more difficult to cause buffer overrun errors. Even on a 32 bit machine, if you allow the string to be the size of available memory, a length prefixed string is only three bytes wider than a null terminated string. On 16 bit machines this is a single byte. On 64 bit machines, 4GB is a reasonable string length limit, but even if you want to expand it to the size of the machine word, 64 bit machines usually have ample memory making the extra seven bytes sort of a null argument. I know the original C standard was written for insanely poor machines (in terms of memory), but the efficiency argument doesn't sell me here. Pretty much every other language (i.e. Perl, Pascal, Python, Java, C#, etc) use length prefixed strings. These languages usually beat C in string manipulation benchmarks because they are more efficient with strings. C++ rectified this a bit with the std::basic_string template, but plain character arrays expecting null terminated strings are still pervasive. This is also imperfect because it requires heap allocation. Null terminated strings have to reserve a character (namely, null), which cannot exist in the string, while length prefixed strings can contain embedded nulls.

其中一些东西比C语言出现得更晚，所以C语言不知道它们是有道理的。然而，在C语言出现之前，有些语言就已经很简单了。为什么会选择空终止字符串，而不是明显更好的长度前缀?

编辑:因为有些人问了关于我上面提到的效率点的事实(他们不喜欢我已经提供的事实)，他们源于以下几点:

使用空结尾字符串的Concat需要O(n + m)时间复杂度。长度前缀通常只需要O(m)。 使用空结尾字符串的长度需要O(n)时间复杂度。长度前缀为O(1)。 Length和concat是迄今为止最常见的字符串操作。在一些情况下，以空结尾的字符串可能更有效，但这种情况发生的频率要低得多。

从下面的答案，这些是一些情况下，空终止字符串更有效:

When you need to cut off the start of a string and need to pass it to some method. You can't really do this in constant time with length prefixing even if you are allowed to destroy the original string, because the length prefix probably needs to follow alignment rules. In some cases where you're just looping through the string character by character you might be able to save a CPU register. Note that this works only in the case that you haven't dynamically allocated the string (Because then you'd have to free it, necessitating using that CPU register you saved to hold the pointer you originally got from malloc and friends).

上面这些词都没有length和concat常见。

下面的答案中还有一个断言:

你需要把绳子的一端剪掉

但这个是不正确的——对于以null结尾的字符串和有长度前缀的字符串，它的时间是相同的。(以Null结尾的字符串只是在你想要的新结尾的地方插入一个Null，长度前缀只是从前缀中减去。)

有没有这样做的方法:

$test_array = array(
    "first_key" => "first_value", 
    "second_key" => "second_value"
);

var_dump(
    array_map(
        function($a, $b) {
            return "$a loves $b";
        }, 
        array_keys($test_array), 
        array_values($test_array)
    )
);

但是不是调用array_keys和array_values，而是直接传递$test_array变量?

期望的输出是:

array(2) {
  [0]=>
  string(27) "first_key loves first_value"
  [1]=>
  string(29) "second_key loves second_value"
}

我不能得到我的头如何部分工作在functools。 我有以下代码从这里:

>>> sum = lambda x, y : x + y
>>> sum(1, 2)
3
>>> incr = lambda y : sum(1, y)
>>> incr(2)
3
>>> def sum2(x, y):
    return x + y

>>> incr2 = functools.partial(sum2, 1)
>>> incr2(4)
5

现在在队列中

incr = lambda y : sum(1, y)

我得到，无论我传递给incr的参数是什么，它都会作为y传递给lambda，它会返回sum(1, y)即1 + y。

我理解。但是我不明白这一点。

在偏函数中，4是如何作为x传递的?对我来说，4应该取代求和2。x和4的关系是什么?

我已经阅读了维基百科上关于过程式编程和函数式编程的文章，但我还是有点困惑。有人能把它归结为核心吗?

最近我读了很多关于函数式编程的东西，大部分我都能理解，但有一件事我就是搞不懂，那就是无状态编码。在我看来，通过删除可变状态来简化编程就像通过删除仪表盘来“简化”一辆汽车:最终产品可能更简单，但希望它能与最终用户交互。

几乎我能想到的每个用户应用程序都将状态作为核心概念。如果你写了一个文档(或一个SO post)，状态会随着每一个新的输入而改变。或者如果你玩电子游戏，会有大量的状态变量，从所有角色的位置开始，这些角色往往会不断移动。如果不跟踪不断变化的值，您怎么可能做任何有用的事情呢?

每次我发现一些讨论这个问题的东西，它都是用真正的技术函数语言写的，假设我没有浓厚的FP背景。有谁知道如何向那些对命令式编码有很好的、扎实的理解，但在函数方面完全是n00b的人解释这一点吗?

编辑:到目前为止，一堆回复似乎试图让我相信不可变值的优点。我懂你的意思。这很有道理。我不明白的是，在没有可变变量的情况下，如何跟踪必须不断变化的值。

我试图按属性排序一些值，就像这样:

a = sorted(a, lambda x: x.modified, reverse=True)

我得到这个错误消息:

<lambda>() takes exactly 1 argument (2 given)

为什么?我该怎么解决呢?

---

这个问题最初是为Python 2.x编写的。在3。TypeError: sorted expected参数为1,got参数为2。

参考透明度是什么意思?我曾听人描述它为“这意味着你可以用等号替换等号”，但这似乎是一个不充分的解释。

I have always thought that functional programming can be done in Python. Thus, I was surprised that Python didn't get much of a mention in this question, and when it was mentioned, it normally wasn't very positive. However, not many reasons were given for this (lack of pattern matching and algebraic data types were mentioned). So my question is: why isn't Python very good for functional programming? Are there more reasons than its lack of pattern matching and algebraic data types? Or are these concepts so important to functional programming that a language that doesn't support them can only be classed as a second rate functional programming language? (Keep in mind that my experience with functional programming is quite limited.)