I, Istarius

Higher Order Messaging in Ruby

Sunday, October 8th, 2006

Having played around with Ruby for some six months now, I feel confident enough to make my first post on the subject. It’s going be about Higher Order Messaging, and it’s more of an expansion on an excellent description by Nat Pryce. I’m writing this post partly because I feel my implementation is a tad better (less cumbersome, as one need not define a class for each new method), and partly because it feels like his post has gone largely unnoticed.

First of all, let’s talk about blocks. Anyone familiar with Ruby will have some knowledge of blocks. Blocks in Ruby is a way to pass a chunk of code as argument to a function; blocks are also full closures, so they may reference any variables that exist in the scope in which they were declared. An example of block usage:

[0,1,2,3,4].select { |val| val.nonzero? }
=> [1,2,3,4]

As you may know, Enumerable#select loops through a collection and returns a new collection containing those elements for which the block evaluates to true. So, the example above produces the array [1,2,3,4], since Numeric#nonzero? will return false for the first element in the array and true for the others.

I expect this is nothing new for most people. Often however, as in the above example, this syntax seems a little verbose.

(more…)

Posted in Ruby | 103 Comments »

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Almost Partial Methods Using Higher Order Messaging

Higher Order Messaging in Ruby

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