Higher Order Messages for Mapping

Trejkaz — Fri, 04 Nov 2005 10:29:00 +1100

Say you want to convert an array of strings to uppercase. You could write

result = names.map { |name| name.upcase }

PragDave suggests an alternative which uses the Ruby Extensions Project’s Symbol#to_proc method to pass a symbol.

result = names.map(&:upcase)

This is all well and good, but can you really call it elegant? Suppose you want to add 1 to all elements in a list. How can this method let you pass in that parameter? It seems that it can’t.

Higher Order Messages (HOM) provide a better way, although a way which seems even more like magic.

The Homer project offers HOM for Ruby, and although it didn’t have a method which did something like map, it was relatively simple to whip something together.

My own version of the above functionality:

result = names.map_using.upcase

Isn’t that better? I couldn’t call it map without causing a little mayhem, having to alias the old version and still provide complete compatibility was a bit much for me at this point in time.

But better yet, this version does permit you to use parameters:

costs_with_gst = costs.map_using * 1.1

Don’t bother asking for the source code for this… I’ll be shuffling it up to the Homer project as soon as I hit submit. ;-)

Trypticon: Higher Order Messages for Mapping

Higher Order Messages for Mapping