155ec7dc41
* Finally added `array-axis-expand' as a dual for `array-axis-reduce' in order to implement `vandermonde-matrix' elegantly * Better, shorter matrix multiply; reworked all matrix arithmetic * Split "matrix-operations.rkt" into at least 5 parts: * "matrix-operations.rkt" * "matrix-basic.rkt" * "matrix-comprehension.rkt" * "matrix-sequences.rkt" * "matrix-column.rkt" Added "matrix-constructors.rkt" Added `matrix', `row-matrix', and `col-matrix' macros A lot of other little changes Currently, `in-row' and `in-column' are broken. I intend to implement them in a way that makes them work in untyped and Typed Racket.
22 lines
836 B
Racket
22 lines
836 B
Racket
#lang typed/racket
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(require math/array
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"matrix-types.rkt"
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"matrix-constructors.rkt"
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"matrix-arithmetic.rkt")
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(provide matrix-expt)
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(: matrix-expt : (Matrix Number) Integer -> (Matrix Number))
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(define (matrix-expt a n)
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(cond [(not (square-matrix? a)) (raise-argument-error 'matrix-expt "square-matrix?" 0 a n)]
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[(negative? n) (raise-argument-error 'matrix-expt "Natural" 1 a n)]
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[(zero? n) (identity-matrix (square-matrix-size a))]
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[else
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(let: loop : (Matrix Number) ([n : Positive-Integer n])
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(cond [(= n 1) a]
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[(= n 2) (matrix* a a)]
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[(even? n) (let ([a^n/2 (matrix-expt a (quotient n 2))])
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(matrix* a^n/2 a^n/2))]
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[else (matrix* a (matrix-expt a (sub1 n)))]))]))
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