From: Ronald Fischer <ronald.fischer@...>
Date: 2007-05-29T16:55:01+09:00
Subject: Re: Introducing the "it" keyword

> > A more
> > general solution could be like this:
> > 
> >   let a+b+c in
> >     let foo=d*e in
> >       let x/y in
> >         puts ($1+foo)*($1-$2)-$2/($1-foo)
> > 
> > Here, $1 would be bound to x/y (innermost unnamed let 
> > binding), $2 would
> > be bound to a+b+c (second innermost unnamed let binding). 

> 
> You're working too hard:
> 
> def let(*args)
>   yield *args
> end
> 
> def use_let(a,b,c)
>   let a+b+c do |it|
>     return it if it < 10
>   end
> end
> 
> use_let(1,2,3) # 6
> use_let(4,5,6) # nil
> 
> No need for additional keywords or even global variables, 
> just a little
> method named let.

With the crucial difference that in your solution, you are *required*
to name the bound variable (here: it), while in my proposal, you are
not.

I think if we only want to introduce an auxiliary variable as
"abbreviation"
for an expression which occurs repeatedly in a block, Ruby indeed has
many
ways to do it, as do most other languages I know. The problem becomes
interesting
IMO if we are libarated from the requirement to invent a name for such a
variable.
The OP suggested to have a "reserved variable" named 'it' which is kind
of 
implicitly bound, but this is a special case for a special type of
programming
pattern. My alternative suggestion go into a more general direction,
where you 
can have more than one binding, and where it is the programmer's choice
whether 
or not to name the variables.

Ronald
-- 
Ronald Fischer <ronald.fischer@venyon.com>
Phone: +49-89-452133-162