From: Yusuke ENDOH <mame@...>
Date: 2011-07-17T09:59:42+09:00
Subject: [ruby-core:38116] Re: [Ruby 1.9 - Feature #4766] Range#bsearch

> How is this useful? It's basically "find minimum" value, right? What difference does it make that it uses a binary search?
>
> If binary searching is important, then why not have a #beach --which can then be used to extrapolate any variety of other methods.

Maybe I'm not sure your point.
It finds minimum value by using binary search.
Does the name `bsearch' matter?  Is `beach' really suitable?



I add a practical example of Range#bsearch for Float domain.
The following code obtains the interior radius between 3 circles
of radii a,b,c that are circumscribed each other, by using law of
cosines three times:

  (0.0 .. [a,b,c].min).bsearch do |t|
    u, v = (t+a+b)*t, a*b
    s  = Math.acos((u - v) / (u + v))
    u, v = (t+b+c)*t, b*c
    s += Math.acos((u - v) / (u + v))
    u, v = (t+c+a)*t, c*a
    s += Math.acos((u - v) / (u + v))
    s <= Math::PI * 2
  end

-- 
Yusuke Endoh <mame@tsg.ne.jp>