Women in Technology

Article:		An Introduction to Haskell, Part 1: Why Haskell
Subject:		List comprehension in python
Date:		2007-05-24 05:33:37
From:		Skink
To filter the even number in Python I would have used : even_list = [i for i in [1,2,3,4,5,6,7,8,9,10] if i % 2 == 0] or even better : even_list = [i for i in range(1,11) if i % 2 == 0]

Showing messages 1 through 5 of 5.

• List comprehension in ruby too...
  2007-05-24 08:11:27  pmccann [View]
  
  
  The ruby's also a little funked: maybe something like...
  
  (1..10).find_all {|i| i % 2 == 0}
• While we're picking apart the examples...
  2007-05-28 14:45:08  Yakshavers [View]
  
  
  The C example takes the cake. How is the caller supposed to know how many elements are in the returned array, so as to avoid a buffer overrun?
• List comprehension in ruby too...
  2007-05-26 03:23:29  paulk_asert [View]
  
  
  The Groovy equivalent to this looks very similar:
  
  (1..10).findAll {i -> i % 2 == 0}
  
  but if you look here:
  
  http://groovy.codehaus.org/Functional+Programming
  
  You can define the infinite stream of natural numbers which then lets you define all the even numbers as follows:
  
  def evennumbers = naturalnumbers.filter{ it % 2 == 0 }
  
  and then use it like this:
  
  assert [2 4 6 8 10] == evennumbers.take(5)
  
• List comprehension in ruby too...
  2007-05-25 12:24:06  PaulBattley [View]
  
  
  You could also do it like this, to make it a bit more explicit:
  
  even = lambda{ |x| x % 2 == 0 }
  (1..10).select(&even)
  
  But it's more elegant in Haskell.

• List comprehension in python
  2007-05-24 07:52:54  llimllib [View]
  
  
  Or, to ape the Haskell functional application:
  
  

  from functools import partial 
  
  def even(n): return n%2 == 0 
  
  
  
  evens = partial(filter, even) 
  
  evens(range(1,11))