From: Joel VanderWerf <vjoel@...>
Date: 2006-05-28T04:31:27+09:00
Subject: Re: Basic ruby looping question

Joel VanderWerf wrote:
> Marston A. wrote:
...
>> for row in @large_row_array WHERE row.element == "something"
>>  ... some some stuff
>> end
...
> So as long as you are working with tests that can be expressed using
> #===, you can use #grep.

In your case, grep may not be so useful after all. You would have to
define an object whose #=== method performs the row.element ==
"something" test.

require 'benchmark'

tester = Object.new
def tester.===(row)
  row.element == 987654
end

class Row
  attr_accessor :element
end

rows = (0..1_000_000).map {|i| r = Row.new; r.element = i; r}

Benchmark.bmbm do |b|
  b.report("grep") do
    rows.grep(tester) {|row|}
  end

  b.report("each-if") do
    rows.each {|row| if row.element == 987654 then nil end }
  end

  b.report("select-each") do
    rows.select {|row| row.element == 987654}.each {|row|}
  end
end

__END__

Rehearsal -----------------------------------------------
grep          0.720000   0.000000   0.720000 (  0.725553)
each-if       0.590000   0.000000   0.590000 (  0.587160)
select-each   0.770000   0.000000   0.770000 (  0.768704)
-------------------------------------- total: 2.080000sec

                  user     system      total        real
grep          0.730000   0.000000   0.730000 (  0.735809)
each-if       0.590000   0.000000   0.590000 (  0.587350)
select-each   0.570000   0.000000   0.570000 (  0.564276)


-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407