[ruby-talk:5592] Re: local variables (nested, in-block, parameters, etc.)

Yukihiro Matsumoto wrote:
> 
> Hi,
> 
> In message "[ruby-talk:5555] Re: local variables (nested, in-block, parameters, etc.)"
>     on 00/10/16, Clemens Hintze <[e-mail]> writes:
> 
> |  { |a, b, c| ... }
> |
> |works as we expect currently, but (in violence of the allowed lexpr) we
> |could allow symbols as well:
> |
> |  { |:a, :b, :c| ... }
> 
> Hmm, changes seems minimal, but I feel symbols as lvalues are less
> self descriptive.
> 
>                                                         matz.

Perhaps my previous post [5548] got lost (or maybe it was too pitiful to answer?),
but it was similar to this except introduced an appended tilde, '~', to denote
that the variable should be treated as block-local, (but with an initial value
equivalent to any matching local variable).

{|a~,b~| ... }

This would allow mixing:

{|a~,b~,c,d| .... }

And would not change how the expressions in the block were formed,
because the tilde would only be used inside the "| |" portion:

{|a~,b~,c,d| a+=1; c=2; print "a=#{a}, c=#{c}" }

I now do not have to keep track of variables outside of the block to avoid
conflicts after the block. :-)

In summary, using |b~| simply means that a new block var named b is created with
the initial value of local var b, if it exists. Nothing else changes. It is mere
syntax sugar to add some control to block scoping.

Thus, it would be easy to tell which variables were new for the block (b~) and 
which were shared locals (c) that continue after the block. 


Am I out in left field, or is this sensible?


Guy N. Hurst

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