通过跳过每 2 个元素来提取块的最优雅方法

Question

假设我有

block: [a 1 b 2 c 3]

我要

[1 2 3]

像这样的东西很笨拙而且不起作用，因为我使用的是单词类型（我希望它是单词而不是字符串）：

  block: [a 1 b 2 c 3]
  block2: []

  counter: -1
  foreach 'element block [
    counter: negate counter
    if counter append block2 element
  ]

Answer 1

EXTRACT 函数应该适合这里的要求：

>> extract/index [a 1 b 2 c 3] 2 2
== [1 2 3]

对于这种类型的东西，它相当通用。

>> help extract
USAGE:
     EXTRACT series width

DESCRIPTION: 
     Extracts a value from a series at regular intervals. 
     EXTRACT is a function! value.

ARGUMENTS:
     series       [series!] 
     width        [integer!] "Size of each entry (the skip)".

REFINEMENTS:
     /index       => Extract from an offset position.
        pos          [integer!] "The position".
     /into        => Provide an output series instead of creating a new one.
        output       [series!] "Output series".

通过跳过每 2 个元素来提取块的最优雅方法

Most elegant way to extract block by skipping every 2 element

rebol

red