I should have added that this is Suse Linux 10.2, amd64 architecture, Gambit Version 4.0 beta 22. Also, problem remains when the receive in nap-join-transforms doesn't have a duplicate value.

Andrew

Hi,

Well, first of all this segfaults: qp6 napito: ./napito-base.scm Segmentation fault which I guess is a bug.

But also, I got a bit carried away trying to remove function calls in matrix multiplication. I'd appreciate some advice - if the code worked, would it be efficient? In particular, do the values/receive pairs get "compiled away"?

I hope the code is fairly obvious - I'm trying to unpack a list with contains the non-zero elements from a typical 2D geometric transform and then do the matrix multiplication on a point.

Thanks, Andrew

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On 18-Aug-07, at 9:13 AM, andrew cooke wrote:

Hi,

Well, first of all this segfaults: qp6 napito: ./napito-base.scm Segmentation fault which I guess is a bug.

Yes it is. The problem is that your code has a syntax error, so the runtime system tries to raise a syntax error exception. Unfortunately there is a bug in this branch when the code was macro expanded, or passed to eval. Anyway, the fix is to replace the line

(head (##source-code (##car code)))

by

(head (##source-code (##sourcify (##car code) src)))

in lib/_eval.scm and then rebuild Gambit with a make.

But also, I got a bit carried away trying to remove function calls in matrix multiplication. I'd appreciate some advice - if the code worked, would it be efficient? In particular, do the values/receive pairs get "compiled away"?

No they don't. The call (values 1 2 3) actually creates a vector- like object, tagged as a multiple-value. So the code is the same efficiency as (vector 1 2 3). You'll get much better optimization by using a CPS-style. This is easy in your case: just pass in the consumer of your values as a parameter, i.e. replace

(define-syntax row1 (syntax-rules () ((_ a b c d e f) (values a b c))))

(receive (x y z) (row1 1 2 3 4 5 6) (list x y z))

by

(define-syntax row1 (syntax-rules () ((_ a b c d e f consumer) (consumer a b c))))

(row1 1 2 3 4 5 6 (lambda (x y z) (list x y z)))

I am considering adding a deforestation optimization to the Gambit compiler to eliminate the construction of multiple-values objects (and pairs, vectors, etc) when it is easy. But that's still under development.

Marc