From: dblack@...
Date: 2007-07-04T23:08:54+09:00
Subject: Re: block params scoping (was ruby-talk 257917: RE: Using a block to surround a string?)

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Hi --

On Wed, 4 Jul 2007, Gregory Brown wrote:

> On 7/4/07, Pe=F1a, Botp <botp@delmonte-phil.com> wrote:
>> Fr David Black:
>> # Method definitions always have their own local scope, so a, b, and
>> # string are strictly local to the method.  Blocks pick up the scope
>> # that they're created in, and can also create variables that weren't
>> # already in that scope.  Those variables disappear when the block
>> # exits; the ones that were there already survive:
>> #
>> #    x =3D 1
>> #    some_method { y =3D x + 1 }   # same x; new y
>> #    y                           # undefined; block's y didn't survive
>> #    x                           # same x
>>=20
>> Hi David,
>>=20
>> How about parameter variables, will its scoping change/stay in ruby2 ?
>>=20
>> Currently,
>>=20
>> irb(main):011:0> x=3D"testing"
>> =3D> "testing"
>> irb(main):012:0> 5.times{|x|}
>> =3D> 5
>> irb(main):013:0> x
>> =3D> 4
>>=20
>> i'd prefer
>>=20
>> x =3D "testing"
>> some_method { |x| y =3D x + 1 }   # different x; overrides any x
>> x                               # =3D> "testing", same x outside
>>=20
>
> Hi, example from Eigenclass[0]:
>
> a =3D 1
> 10.times{|a| } # !> shadowing outer local variable - a
> a  # =3D> 1
>
> looks like it throws a warning and behaves as we all want it to. :)

I actually like the current behavior, but I think I'm in a minority of
two (me and Guy Decoux, as I recall).  I don't like the warning thing.
If the whole point is to make life easy for people who cut-and-paste
code blocks and don't want to check the names of the variables (which
I don't do, but I gather that's what people want to do), then it
should be totally ignored.  A warning means you have to go in and
change it, which is what you have to do now.  So I don't see any gain.


David

--=20
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