Forwarded with the permission of Stephen Watt.
On 05/13/2008 05:30 PM, Stephen Watt wrote:
> Hi Ralf,
>
> For does not introduce a new scope for its body for a few reasons:
>
> 1. In languages like C any compound statement is a new scope so we
> have new scopes for loop bodies, branches of if-s etc.
>
> This does not interact well with implicitly local variables.
>
> If a new variable is by default local to the smallest enclosing
> scope, then new variables would be visible only in overly small
> regions.
>
> E.g. suppose compound statements were scopes, then
>
> if foo? then a := 1 else { f(); a := 2 }
>
> would give unexpected results.
>
>
> 2. It is convenient to be able to test the last value that a for loop
> index reached.
>
> 3. Since the language allows goto, it is useful to be able to reduce
> structured control flow to the goto case.
>
> I admit that none of these are absolutely compelling. So I should add
> that we tried it the other way, and this way made coding the library
> easier.
>
> -- Stephen
>
>
>
>
> On Tue, May 13, 2008 at 05:13:53PM +0200, Ralf Hemmecke wrote:
>> Dear Stephen,
>>
>> could you give a comment about the background of "local" and "free"
>> in Aldor and why "for" does *not* introduce a new scope for its body.
>>
>> Thank you
>> Ralf
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