From: "Ara.T.Howard" <ahoward@...>
Date: 2004-04-21T11:34:07+09:00
Subject: Re: efficient collect+compact ?

On 21 Apr 2004, Martin Pirker wrote:

> Hello...
> 
> What's the most efficient way for
> 
> puts [1,2,3,4,5,6,7,8,9,10].collect{ |x| next if x % 2 == 0; x+10 }.compact
> or
> puts [1,2,3,4,5,6,7,8,9,10].collect!{ |x| next if x % 2 == 0; x+10 }.compact!
> 
> Or:
> I want to iterate over all array elements, process them, decide
> whether the result is any good, and keep only the good ones.
> It's ok doing that by chaining collect+compact, but I ponder this must
> be slow/inefficient for array with xxxxx elements.


doesn't seem to make much difference:

~ > time ruby -e '(1..ARGV.shift.to_i).to_a.collect{|x| next if x % 2 == 0; x+10 }.compact' 1048576

real    0m1.496s
user    0m1.480s
sys     0m0.020s

~ > time ruby -e '(1..ARGV.shift.to_i).to_a.collect!{ |x| next if x % 2 == 0; x+10 }.compact!' 1048576

real    0m1.396s
user    0m1.390s
sys     0m0.000s


suprising.

> I read Array and Enumerable docs, have I missed something[1] or does
> a straight "collect everything but nil" function not exist?
> 
> Martin
> 
> [1]
> (it's already past 3am but I remember searching the same thing sometime ago)
> 

-a
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