From: Christoph <chr_news@...>
Date: 2002-09-24T22:40:43+09:00
Subject: Re: are functions/methods "first class objects"?

"Christian Szegedy"
....
> > k =    35
> > a = lambda {|x,y|    [k + 2 * x, k +  3 * x]  }
> > b = lambda {|t,s|    t + s    }
> >
> > c = b * c
> >
> > c[1,1]  = = 75  # true
> > ---
>
> I don't understand your example. I guess, you wanted to
> write
> c = b*a

Yes - sorry ...

> but what do you expect to be the result of the composition
> of a two variable function and a two variable function?
> A two variable function returning a one variable function?
> But this does not match your example...
> Perhaps you wanted to write c[1,1][k] == 75 ?

No I really mend

c[1,1] == 75   # in a pestrian way

---
 k =    35
  a = lambda {|x,y|    [k + 2 * x, k +  3 * x]  }
 b = lambda {|t,s|    t + s    }

c = lambda {|_t,_s|   b[*a[_t,_s]]  }

p c[1,1] # 75
---


>
> > - this should work with essentially all  in and out going
> > arities.  Of course one can do it but it is more tedious
> > then you might think (which was my sole point) .
>
> OK, I admit that in this generality it is not so simple in
> Ruby as in (***)ML.
>
> Now, let us be honest, is it so important? I do a lot of
> meta-programming, but I have never encountered a situation
> requiring such a high level approach.

I guess this (and other functional ``deficiencies'')  is (are) not
important since Ruby is probably more  of an ``functionally
enhanced imperative language'' -  so any potential weakness
of Rubys functional side are well taken care of by its
strong imperative meta features.


/Christoph