From: Johann Hibschman <johann@...>
Date: 2001-03-14T13:10:02+09:00
Subject: [ruby-talk:12598] Re: FEATURE REQUEST: 'my' local variables

Stephen White writes:

> *** start of loony tunes proposal ***

Understood.  Start of relatively newbie comments.  :-)

> The "i" is protected because it's defined in the |i| parameter list. This
> is a nice way of just using a name for the loop without trashing anything
> else. All other variables are just there and used, like BASIC. :)

Okay.  This here is the biggest source of errors for me in irb.  In
real programs, I can avoid it, but in interactive use, I have trouble.
Namely, I keep expected the variable in blocks to introduce a new
local variable, like a function call.

i.e. I type
x = [1, 2, 3, 4, 5]
y = x.collect{|x| x**2}

And suddenly, I've overwritten x.  Maybe this is my lispy heritage
showing, but I just don't expect this behavior.  The block looks like
a function call, so I expect it to introduce a new local.

Likewise, I expect variables inside the block to refer to the outer
scopes by default, by analogy to scheme/lisp lexical scoping
conventions.

It would be nice to have the equivalent of Scheme's "let", i.e. a way
to explicitly introduce new locals, but I don't really need it.

How about a let-form like those of the ML languages?  i.e.

let x=10, y, z=27 in
  p x
  y = x*20
  ... etc ...
end

where the intention is that all the variables named in the let form
are taken as local variables which shadow any other similarly-named
variables in scope.

That just somehow seems cleaner to me.

-- 
Johann Hibschman                           johann@physics.berkeley.edu