Re: [PATCH] Fast R6RS div/mod; improved extensibility of numerics

[Andy Wingo <wingo@pobox.com>]

On Mon 31 Jan 2011 18:35, Mark H Weaver <mhw@netris.org> writes:

> Andy Wingo <wingo@pobox.com> writes:
>>> The last patch might be slightly controversial.  Although it does not
>>> make `integer-expt' a generic function, nonetheless it can now
>>> exponentiate _any_ scheme object that can be multiplied using `*'.
>>
>> To me this is fine, in principle; but I wonder about causing `(expt #t
>> 0)' to produce 1.  It seems that in any case the range of the output
>> should be continuous -- i.e. if (expt <my-matrix> 1) produces a matrix,
>> and (expt <my-matrix> n) for n > 1 makes a matrix, then (expt
>> <my-matrix> 0) should also produce a matrix.  Or no?
>
> When using generic arithmetic operators, there's no way to return
> objects of the correct type in all corner cases like this.

I did apply it, but it made the test cases start to fail, because
numbers.test is loaded after ecmascript.test, and:

    scheme@(guile-user)> ,L ecmascript
    Happy hacking with ECMAScript!  To switch back, type `,L scheme'.
    ecmascript@(guile-user)> true * true;
    $1 = 1
    ecmascript@(guile-user)> ,L scheme
    Happy hacking with Scheme!  To switch back, type `,L ecmascript'.
    scheme@(guile-user)> (* #t #t)
    $2 = 1

I think that's the thing, anyway.  It just sounds really squirrelly.
Could you not extend `expt' or `integer-expt' instead?

Andy
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