PTC and "SHOULD" vs "MUST"

Mark S. Miller erights at google.com
Thu Jun 2 00:37:46 PDT 2011


It wasn't just a thinko, but I'm actually happier with MUST. Fixed.

On Wed, Jun 1, 2011 at 3:42 PM, Brendan Eich <brendan at mozilla.com> wrote:

> Thanks for catching this, it goes back to
> http://wiki.ecmascript.org/doku.php?id=strawman:proper_tail_calls&rev=1273414092(first rev). Cc'ing Mark. I bet it is just a thinko for MUST and we can fix
> it quickly.
>
> /be
>
> On Jun 1, 2011, at 3:36 PM, Peter Michaux wrote:
>
> > http://wiki.ecmascript.org/doku.php?id=harmony:proper_tail_calls
> >
> > I notice that in the proper tail calls wiki page that a compliant
> > interpreter "SHOULD implement a call in proper tail position as a
> > PTC." In order for a programmer to use proper tail calls for
> > arbitrarily deep recursion, the programmer needs a guarantee that the
> > interpreter will use proper tail calls. This would mean the "SHOULD"
> > needs to be a "MUST". Otherwise what does the proper tail calls
> > proposal gain the programmer?
> >
> > For example, R5RS has much stronger language compared with "SHOULD"
> > about Scheme using proper tail calls.
> >
> > "Implementations of Scheme are required to be properly tail recursive."
> >
> > With that language the programmer using Scheme can then depend on that
> feature.
> >
> > Peter
> > _______________________________________________
> > es-discuss mailing list
> > es-discuss at mozilla.org
> > https://mail.mozilla.org/listinfo/es-discuss
>
>


-- 
    Cheers,
    --MarkM
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