From: Brian Candler <b.candler@...>
Date: 2009-02-03T20:29:13+09:00
Subject: Re: choose parameter to solve for

Jason Lillywhite wrote:
> I'm looking for a clean way to write a function that allows me to choose
> which parameter to solve for assuming all others are known. Is it good
> design to do something like this: ?
> 
> class Foo
>   def initialize(x, y, z)
>     @x, @y, @z = x, y, z
>   end
> 
>   def function(var)
>     if @x.nil?
>       @x = var
>     elsif @y.nil?
>       @y = var
>     else
>       @z = var
>     end
>     @x + @y + @z
>   end
> 
> end
> 
> z = Foo.new(1, 2, nil)
> z.function(3)
> => 6

Hmm, is this some sort of currying?

  adder = lambda { |x,y,z| x+y+z }
  z = lambda { |z| adder[1,2,z] }
  z[3]

You could perhaps factor this out into some sort of fix_args method.

Ruby 1.9 has Proc#curry, but I think this only fixes from the left.

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