From: Steven Lumos <steven@...>
Date: 2007-03-27T08:58:54+09:00
Subject: Re: Backus, Functional Programming, and Ruby

Devin Mullins <twifkak@comcast.net> writes:

> Jesse Merriman wrote:
>> On Sunday 25 March 2007 18:03, Joel VanderWerf wrote:
>>
>>>Ruby has its own way of doing things, not that there is anything wrong
>>>with defining new ways:
>>>
>>>[[1,2,3], [6,5,4]].transpose.map{|x,y|x*y}.inject{|s,x|s+x}
>>>=> 28
>>
>> Yep, I was just seeing how close I could make Ruby code look like
>> Backus' code; the goal was to define inner_product as a compose of
>> the three other functions without any named variables.
>
> module Enumerable
>   def inner_product
>     transpose.map(&:*).inject(&:+)
>   end
> end
>
> :P
>
> (Not to slight Backus. Functional programming and BNF are both totally
> cool.)

That's the most morphologically equivalent to Lisp Ruby ever!

(defun inner_product (matrix)
  (reduce '+ (mapcar '* (transpose matrix))))

I'm rusty, but still...

Steve