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-rw-r--r--determ.scm14
1 files changed, 14 insertions, 0 deletions
diff --git a/determ.scm b/determ.scm
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--- /dev/null
+++ b/determ.scm
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+;"determ.scm" Determinant
+
+(define (determinant m)
+ (define (butnth n lst)
+ (if (zero? n) (cdr lst) (cons (car lst) (butnth (+ -1 n) (cdr lst)))))
+ (define (minor m i j)
+ (map (lambda (x) (butnth j x)) (butnth i m)))
+ (define (cofactor m i j)
+ (* (if (odd? (+ i j)) -1 1) (determinant (minor m i j))))
+ (define n (length m))
+ (if (eqv? 1 n) (caar m)
+ (do ((j (+ -1 n) (+ -1 j))
+ (ans 0 (+ ans (* (list-ref (car m) j) (cofactor m 0 j)))))
+ ((negative? j) ans))))