From: Dave Thomas <Dave@...>
Date: 2001-05-11T13:38:11+09:00
Subject: [ruby-talk:14975] Re: Array search idiom

"James B. Crigler" <james.b.crigler@lmco.com> writes:

> 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?
...
> 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"
> ]
> 
> first_group_of_primates = Array.new
> a.each do |line|
>     next unless line =~ /^primates\./ .. false
>     break if line !~ /^primates\./
>     first_group_of_primates.push line
> end

I don't know if this is better, and it still has the extra pattern
match on the first element of the matching subarray, but it's a
slightly different approach.

 start = len = 0
 pat = /^primates\./

 start += 1  while a[start] and a[start] !~ pat
 len   += 1  while a[start+len] =~ pat

 first_group = a[start, len]


Regards


Dave