Re: [Axiom-developer] RE: algebra Makefiles with explicit dependencies, bootstrap, fixed-points etc.

[Stephen Wilson]

Tim, 

I compleatly fine with the fixnum declaration. We just need to make
sure it is a rule programmers can rely on. Consider:

)abbrev package ITER Iter
Iter(): E == I where
  E == with
    iter: () -> Void
  I == add
    iter(): Void == 
      for i in 2.. repeat
         print(i::OutputForm)


The relavent lisp decalres we are using fixnums:

      (LETT |i| (QSADD1 |i|) |ITER;iter;V;1|)


Now compile the above with a lower bound of 3:

      for i in 3.. repeat
         print(i::OutputForm)


We get generic arithmetic:

      (LETT |i| (+ |i| 1) |ITER;iter;V;1|)


Baffled,
Steve


On Mon, Jan 17, 2005 at 12:23:36PM -0500, root wrote:
> Steve,
> 
> I don't know if there is an actual statement to the effect that
> the upper bound on a loop would be a register-sized number (32
> or 64 bits) but at 6Mhz it seemed impossible that one could 
> run a loop of any consequence for greater than 2^32 or 2^64
> iterations. If you wanted to do that you'd have to do the
> looping using some other construct. In general it is safe to
> assume that the upper bound of the register size cannot be
> exceeded. There is a practical performance difference to
> be gained by using (declare (fixnum  as the compiler can,
> in the best case, assign a register to the loop variable.
> 
> t