From: Robert Feldt <feldt@...>
Date: 2001-11-30T14:10:33+09:00
Subject: [ruby-talk:27024] Re: first class functions in Ruby

On Fri, 30 Nov 2001, MikkelFJ wrote:

> 
> "Ralph Mason" <ralph.mason@telogis.com> wrote in message
> news:135701c1792a$679ffc90$0101a8c0@p3...
> > irb(main):010:0> def sq(x)
> > irb(main):011:1> x+x
> > irb(main):012:1> end
> > nil
> > irb(main):013:0> def aMes(f)
> > irb(main):014:1> send(f,42) + send(f,27)
> > irb(main):015:1> end
> > nil
> > irb(main):016:0> aMes :sq
> > 138
> > irb(main):017:0>
> >
> 
> That is nice. It has the same level of compactness that I asked for.
> The :sq handles the problem of delayed evalution.
> I'd still like to be able to simply apply the parameters:
>   f(42)
> but it isn't too bad.
> What remains then is partial evaluation:
> 
Something along the lines:

class Fun
  def initialize(&b)
    @b, @as = b, []
  end
  def [](*args)
    if @as.length + args.length < @b.arity
      @as = @as.concat args
      res = self
    else
      res = @b.call(*(@as + args))
    end
    res
  end
end

def aMes(f)
  f[3] + f[4]
end

sq = Fun.new {|x,y| x*y}

p aMes(sq[2])   #=> 14

?

It's not perfect since arity might surprise sometimes and there are other
issues...

/RobertF