From: Stephen White <spwhite@...>
Date: 2001-05-11T17:02:51+09:00
Subject: [ruby-talk:14984] Re: Array search idiom

On Fri, 11 May 2001, James B. Crigler wrote:

> Here's a question about a ruby idiom.  I have an array that contains
> lines with mammal (classification. animal) pairs like the one found
> in the code snippet.  I need to find the first contiguous list of
> primates.  Assuming the array is called "a", here's how I solved the
> problem.  This does what I want, but is there a better way?

My take on this is that you're trying to work with insufficiently
massaged data. Convert the array into a more useable form first.

> a = [
> "insectivora. shrews", "insectivora. moles", "insectivora. hedgehogs",
> "dermoptera. flying lemurs", "chiroptera. bats", "primates. tree shrews",
> "primates. lemurs", "primates. monkeys", "edentata. sloths",
> "edentata. armadillos", "edentata. anteaters", "pholidota. scaly anteaters",
> "primates. marmosets", "primates. great apes", "primates. humans",
> "lagomorpha. hares", "lagomorpha. rabbits", "lagomorpha. pikas",
> "rodentia. mice", "rodentia. rats"
> ]

Let's convert this to a Hash, using classifications.

  b = {}
  a.each {|i|
    group, animal = i.split /\, /
    b[group] ||= []
    b[group] << animal
  }

That gives you the more friendly form of:

  b = {
    "chiroptera"=>["bats"], "rodentia"=>["mice", "rats"],
    "lagomorpha"=>["hares", "rabbits", "pikas"],
    "dermoptera"=>["flying lemurs"],
    "insectivora"=>["shrews", "moles", "hedgehogs"],
    "primates"=>["tree shrews", "lemurs", "monkeys", "marmosets", "great apes", "humans"],
    "edentata"=>["sloths", "armadillos", "anteaters"],
    "pholidota"=>["scaly anteaters"]
  }

So if you want all primates, you can just do:

  b['primates']

and get:

  ["tree shrews", "lemurs", "monkeys", "marmosets", "great apes", "humans"]

in return.

-- 
  spwhite@chariot.net.au