From: Daniel Carrera <dcarrera@...>
Date: 2003-01-15T08:33:01+09:00
Subject: Extracting elements from an array.

Hello,

I have a question about Enumerable#grep or perhaps Enumerable#map.

I have an array and I want to extract the entries that follow certain
criteria.  I'd like to do something like:

array.grep { |x| valid?(x) }
or
array.map { |x| valid(x) ? x : return }

valid?() returns true or false depending on whether the input meets
the criteria.

In my particular problem I have an array of the form:

[ [ 34, "something" ] , [ 2, "another"] , ... ]

I wish to eliminate the entries whose numeric value is less than - say -
3.  So something like:

array.map { |x| x < 3 ? return : x }

would be nice.

I haven't figured out how to do this with either grep or map.  Can anyone
offer some advice?

Thanks a lot,
Daniel Carrera
Graduate Teaching Assistant.  Math Dept.
University of Maryland.  (301) 405-5137