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Re: generic functions
- To: Mikael Djurfeldt <mdj at mdj dot nada dot kth dot se>
- Subject: Re: generic functions
- From: Dirk Herrmann <dirk at ida dot ing dot tu-bs dot de>
- Date: Tue, 4 Apr 2000 15:08:57 +0200 (MEST)
- cc: Guile Mailing List <guile at sourceware dot cygnus dot com>, djurfeldt at nada dot kth dot se
On 4 Apr 2000, Mikael Djurfeldt wrote:
> Dirk Herrmann <dirk@ida.ing.tu-bs.de> writes:
>
> > A quick hack would simply unpack the 'gf', thus still assuming that
> > a zero content indicates an uninitialized state.
>
> I think we should do this for now. Please also make a note about this
> special use of the pointer 0 at some appropriate place in tags.h so
> that we know about this if we change the representation in the future.
>
> (I can imagine that other Guile developers may want to pay an extra
> instruction + memory access for increased cleanliness---please say so
> then---but for me the above is OK.)
Why an extra memory access? You have to read the SCM value to see whether
it is zero, too. The typical alternative initialization values like
SCM_BOOL_F or SCM_UNDEFINED have integer values of 8564 and 9588, which
both fit into 16 bit. I assume that 16 Bit immediates should be available
on many 32 Bit architectures?
Best regards
Dirk Herrmann