From: Dave Burt <dave@...>
Date: 2006-05-21T12:06:32+09:00
Subject: Re: rubynuby - confused by method name "inject"

Jeff Pritchard wrote:
> Can anybody explain to me how the Enumberable#inject method is 
> "injecting" something into something?  I find it very difficult remember 
> method names when I don't "get" them.  So far in Ruby, "inject" takes 
> the cake for least understandable method name (with my own particular 
> convoluted gray matter).
> 
> Can somebody give some examples of its use and state in words how it is 
> "injecting" something into something?

["foo", "bar"].inject(5) {|total, word| total + word.length } #=> 11

This example injects the result of the block applied to each element of
the collection into a single value.

I actually prefer the Haskell term, "fold" -- it repeatedly folds the
function of the value and an element of the collection back into the value.

> If anybody wants to take a stab at "collect", that would be welcome 
> also.

I use "map", which is an alias of "collect".

ys = xs.map {|x| x * x }

It takes a block (a mapping from X to Y) and applies it to a collection
of Xs to map them to Ys.

Cheers,
Dave