This looks like an instance of the problem Neil reported on Monday. I'll discuss Neil's solution with Sam.
Vincent At Thu, 3 Jan 2013 18:47:56 +0100, Jens Axel Søgaard wrote: > > Ignore the previous example. Here is the example again, now > with correct usage of case-lambda. The for/sum problem remains. > > /Jens Axel > > > #lang typed/racket > (require math) > > (: matrix-solve-upper > (All (A) (case-> > ((Matrix Real) (Matrix Real) -> (Matrix Real)) > ((Matrix Real) (Matrix Real) (-> A) -> (U A (Matrix Real))) > ((Matrix Number) (Matrix Number) -> (Matrix Number)) > ((Matrix Number) (Matrix Number) (-> A) -> (U A (Matrix > Number)))))) > (define matrix-solve-upper > ; solve the equation Ux=b > ; using back substitution > (case-lambda > [(U b) > (define (default-fail) > (raise-argument-error > 'matrix-solve-upper > "The upper triangular matrix is not invertible." 0 U)) > (matrix-solve-upper U b default-fail)] > [(U b fail) > (define m (matrix-num-rows U)) > (define x (make-vector m 0)) > (for ([i (in-range (- m 1) -1 -1)]) > (define bi (matrix-ref b i 0)) > (define Uii (matrix-ref U i i)) > (when (zero? Uii) (fail)) > (define x.Ui (for/sum ([j (in-range (+ i 1) m)]) > (* (matrix-ref U i j) (vector-ref x j)))) > (vector-set! x i (/ (- bi x.Ui) Uii))) > (vector->matrix m 1 x)])) > > (define U (matrix [[4 -1 2 3] > [0 -2 7 -4] > [0 0 6 5] > [0 0 0 3]])) > (define b (col-matrix [20 -7 4 6])) > b ; expected > (define x (solve-upper-triangular U b)) > (matrix* U x) > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev _________________________ Racket Developers list: http://lists.racket-lang.org/dev
