Re: (declare (type fixnum ---)) considered etc.

[shebs%utah-orion@utah-cs.arpa (Stanley Shebs)]

In article <8607241621.AA03430@hplsny> snyder%hplsny@hplabs.HP.COM (Alan Snyder) writes:

>I think the PL/I experience shows
>that if you force people to declare the number of bits of
>precision they want, in most cases they will find out what number
>produces the best results on their current machine and use that,
>thus making their programs non-portable in terms of efficiency.

This is a red herring.  Almost everything in CL is going to vary
in efficiency between implementations.  Consider FUNCALL - some impls
do it almost as well as a direct call, while others cons up a list
of arguments and feed to APPLY.  This has a direct bearing on the
efficiency of using things like MEMBER's keyword arguments.  Consider
generic sequence functions, whose allowed variation is notorious;
DELETE is not even required to be destructive!  Consider arrays, which
can be specialized in a dozen ways, or not at all.

As a language, Common Lisp can promise consistent efficiency or consistent
behavior - and I prefer the latter.  It might be possible to promise both in
a high-level language, but nobody's succeeded yet...

								stan