Jupyter 内核

Jupyter Notebook 可以利用任何实现了 Jupyter 消息协议 的程序内核来执行代码。目前已有适用于 Python、Julia、Ruby、Haskell 以及 许多其他语言 的内核。

在本笔记本中，演示如何使用 Coconut 编程语言 执行代码。Coconut 是 Python 的变体，专为 简洁、优雅、Pythonic 的函数式编程 而构建。

在第一个示例中，将定义递归的 factorial 函数，这是一种根本上的函数式方法，不涉及任何状态变化或循环：

def factorial(n):
    """Compute n! where n is an integer >= 0."""
    case n:
        match 0:
            return 1
        match x is int if x > 0:
            return x * factorial(x-1)
    else:
        raise TypeError("the argument to factorial must be an integer >= 0")

3 |> factorial |> print

CoconutSyntaxWarning: deprecated case keyword at top level in case ...: match ...: block (use Python 3.10 match ...: case ...: syntax instead) (line 3)
  /~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

  case n:
      match 0:
          return 1
      match x is int if x > 0:
          return x * factorial(x-1)
  else:
      raise TypeError("the argument to factorial must be an integer >= 0")

  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|

CoconutSyntaxWarning: found deprecated isinstance-checking 'x is int' pattern; rewrite to use class patterns (try 'int(x)') or explicit isinstance-checking ('x `isinstance` int' should always work) (line 6)
        /~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

  match x is int if x > 0:
      return x * factorial(x-1)
  else:
      raise TypeError("the argument to factorial must be an integer >= 0")

  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|

6

尽管这个示例非常简单，但模式匹配是 Coconut 最强大且最复杂的功能之一。

在第二个示例中，实现了快速排序算法。这个 quick_sort 算法使用了一系列新的语法结构：

def quick_sort(l):
    """Sort the input iterator using the quick sort algorithm."""
    match [head] :: tail in l:
        tail = reiterable(tail)
        yield from quick_sort(left) :: [head] :: quick_sort(right) where:
            left = (x for x in tail if x < head)
            right = (x for x in tail if x >= head)
    # By yielding nothing if the match falls through, we implicitly return an empty iterator.

[3,0,4,2,1] |> quick_sort |> list |> print

[0, 1, 2, 3, 4]

最后，看到异常是如何被引发的

x

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
Cell In[3], line 1
----> 1 x  #1: x

NameError: name 'x' is not defined