List comprehension in Ruby

Question

To do the equivalent of Python list comprehensions, I'm doing the following:

some_array.select{|x| x % 2 == 0 }.collect{|x| x * 3} 

Is there a better way to do this...perhaps with one method call?

Answer 1

How 'bout:

some_array.map {|x| x % 2 == 0 ? x * 3 : nil}.compact 

Slightly cleaner, at least to my taste, and according to a quick benchmark test about 15% faster than your version...

Answer 2

If you really want to, you can create an Array#comprehend method like this:

class Array   def comprehend(&block)     return self if block.nil?     self.collect(&block).compact   end end  some_array = [1, 2, 3, 4, 5, 6] new_array = some_array.comprehend {|x| x * 3 if x % 2 == 0} puts new_array 

Prints:

6 12 18 

I would probably just do it the way you did though.