Re: early termination for `map'

[Ludovic Courtès]

Hello!

Andy Wingo <address@hidden> writes:

> If you call `map' or `for-each' with more than one list, our versions of
> these operators will detect if the lists are of unequal length, and
> throw an error in that case.
>
> However, SRFI-1 has long provided an extension to this, to allow for
> early termination when any of the lists runs out.  R6RS adopted this,
> and it looks like R7RS will ratify that.
>
> So perhaps it's time for us to change as well.

To change the default ‘map’ & ‘for-each’ to do like SRFI-1’s, right?

> This would also allow us to get rid of the hack in srfi-1.c in which,
> when and if GOOPS gets loaded, srfi-1 extends the `map' and `for-each'
> primitive generics with its own early-termination code, which in effect
> gives early termination to every `map' user, regardless of whether that
> module has imported srfi-1 or goops.  Sometimes I think that Mikael put
> the Oops in Goops for a reason ;-)

Heh.  :-)

Code not using GOOPS can tell the difference between the default and
SRFI-1 versions, and it can arrange to explicitly use one or the other.
So changing the default versions would be an incompatibility—arguably
not an important one, but still maybe enough to wait until 2.2?

Thanks,
Ludo’.