From: Christophe Grandsire <christophe.grandsire@...>
Date: 2005-10-12T15:48:56+09:00
Subject: Re: Default argument values for blocks

Selon Eric Mahurin <eric_mahurin@yahoo.com>:

>
> Would you consider having something like a begin/end block
> having this ability too?
>
> b=1
> begin(b)
>   b=5
>   p b # => 5
> end
> p b # => 1
>

Interesting. This syntax and the meaning of it remind me of METAFONT's way of
declaring scope (I seem to be one of the few people on Earth besides Knuth who
know a bit of METAFONT, and that's too bad because the language has some
interesting features). In METAFONT (which is structured but not oo) scoping and
subroutine definitions are completely separate. In other words you have to scope
explicitly when you want a new scope. You do that through (surprisingly enough
;) ) a "begin... end;" block. In the block, all variables from the outside
scope are known, so if you want to reuse the name of one of those locally you
have to explicitly "save" it first. So in METAFONT your example would read:

b=1;
begin
  save b;
  b=5;
  message b % => 5
end;
message b; % => 1

I must say I like the "save b" syntax. If begin/end blocks in Ruby are to have
the same ability, it may be an idea (I personally find "begin(b)" unclear. It
looks more to me like you're starting a block somehow indicated by a kind of
label "b" or something like that ;) ).
--
Christophe Grandsire.

http://rainbow.conlang.free.fr

It takes a straight mind to create a twisted conlang.