From: Andrew Wagner <wagner.andrew@...>
Date: 2010-08-28T01:14:25+09:00
Subject: Re: Avoiding eval

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Err, I think I wasn't very clear in my last email, so I'll say it in a
benchmark this time.

require 'benchmark'

Benchmark.bm do |b|


  b.report "using eval" do
    1_000_000.times { eval "Math" }
  end

  b.report "using const_get" do
    1_000_000.times { Kernel.const_get "Math" }

  end

  b.report "using eval on Math::PI" do
    1_000_000.times { eval "Math::Pi" }

  end

  b.report "using const_get injection on Math::PI" do
    1_000_000.times { "Math::PI".split("::").inject(Object) { |cl,n|
cl.const_get n } }

  end

end

using eval 6.5
using const_get 1.297
using eval on Math::Pi 6.875
using const_get injection on Math::PI 18.65

Without the performance benefit, it seems like there's not much benefit in
avoiding eval :(.

On Fri, Aug 27, 2010 at 11:48 AM, Andrew Wagner <wagner.andrew@gmail.com>wrote:

> Well, sure. That's a good point. But now you're taking 3 times as long as
> eval, instead of 1/5 the time, according to my tests.
>
> On Fri, Aug 27, 2010 at 11:40 AM, Robert Klemme
> <shortcutter@googlemail.com>wrote:
>
> > On 27.08.2010 17:24, Andrew Wagner wrote:
> >
> >  If I have a string like "Math", I know I can use const_get to turn it
> into
> >> an instance of Class. Awesome.
> >>
> >> But what if I have something like "Math::PI". Am I stuck using eval to
> >> resolve that?
> >>
> >
> > One typical idiom looks like this:
> >
> > a_class = str.split('::').inject(Object) {|cl,n| cl.const_get n}
> >
> > Cheers
> >
> >        robert
> >
> > --
> > remember.guy do |as, often| as.you_can - without end
> > http://blog.rubybestpractices.com/
> >
> >
>

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