On Thu, 2002-07-04 at 11:19, Andy Wardley wrote:
> On Tue, Jul 02, 2002 at 03:20:35PM -0500, Dan Sugalski wrote:
> > I'm pretty sure the iterators they build are just closures with named
> > arguments, and behave as any other closure would behave.
>
> Not quite. Ruby iterators expect a block. This is very much like a closure
> except that block parameters are local to the scope in which the block is
> defined, not lexically scoped within the block.
>
> Or in other words, any existing variable of the same name as a block parameter
> will be updated when the block is called.
>
> An example:
>
> n = 10
>
> def twice
> yield 1
> yield 2
> end
>
> twice { |n| puts "Hello World #{n}" }
>
> puts "n is now #{n}"
>
> The result of this is:
>
> Hello World 1
> Hello World 2
> n is now 2
>
> I personally believe this approach is flawed, especially considering the fact
> that there is no way (that I know of) to force block parameters to be truly
> lexically scoped or temporary (i.e. 'my' or 'local' in Perlspeak). Much too
> easy to mangle existing variables like this.
>
Most people agree. In the future there will be a way of doing that.
Matz himself has said so.
/Erik
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