From: Mark Slagell <mslagell@...>
Date: 2000-10-16T00:27:04+09:00
Subject: [ruby-talk:5549] Re: Some newbye question

ts wrote:
> 
> >>>>> "D" == Dave Thomas <Dave@thomases.com> writes:
> 
> D>     iterate { <i, j> ...  }     # 'i' is always block local
> 
>  I prefer this rather than the original proposition (1)
> 
> Guy Decoux

As Dave says, params are really placeholders; they behave as pronouns as
opposed to nouns, and we all know that in everyday language, pronouns
carry an assumption of local scope.  To say "whenever I get a personal
letter, I open it" introduces no ambiguity about "it" - we don't have to
worry what the word means at other points in a larger conversation, and
the sentence can be grasped and reasoned about in isolation.  Removing
that assurance in a programming language context, esp. with iterators
("for each thing in this set, do such and such with it"), makes it
harder to be confident about unintended side effects, so that you have
to keep track of what parameter names have been used when you start
nesting procs.

So I guess what I'm saying is that I'd encourage making block params
local.  On the other hand I don't have a lot of old code that it would
break.  If <> and || were given these different scope meanings, it would
be okay too, I'd just use <> all the time. :-)

  Mark