From: Sean O'Halpin <sean.ohalpin@...>
Date: 2005-10-19T23:31:45+09:00
Subject: Re: Array.sort when it's items are String inheritors with redefined <=> works like if not redefined

On 10/19/05, Ara.T.Howard <Ara.T.Howard@noaa.gov> wrote:
> this avoids calling to_i, to_f, or whatever multiple times on the same object,
> which will occur if you use either a spacship (<=>) operator or sort_by
> approach.

I thought sort_by was a packaged form of the Schwartzian transform, i.e.

class A
  def to_i
    puts "in A.to_i"
    3
  end
end

p [1, 2, 3, 4, 5, A.new].sort_by {|x| x.to_i }
# is equivalent to
p [1, 2, 3, 4, 5, A.new].map{|x| [x.to_i, x]}.sort{|y, z| y[0] <=>
z[0]}.map{|x| x[1]}

__END__
in A.to_i
[1, 2, 3, #<A:0x2870f28>, 4, 5]
in A.to_i
[1, 2, 3, #<A:0x2870cd0>, 4, 5]

Regards,

Sean