#lang racket/base
(require racket/vector)
(provide (all-defined-out))
;;; YAML - Yet Another Matrix Library - a SlowThought Production.

;;; racket style vector-like operations
;; Constructors
(define(make-matrix m n [initialize null])
  (let [(vov (make-vector m))] ; vov = vector of vectors   
    (if (null? initialize)
        (for [(i (in-range m))]
          (vector-set! vov i (make-vector n)))
        (for [(i (in-range m))]
          (vector-set! vov i (make-vector n initialize))))
    vov))

(define (build-matrix m n initialize)
  (let [(vov (make-vector m))]
    (for [(i (in-range m))]
      (vector-set! vov i (build-vector n (lambda (j) (initialize i j)))))
    vov))

; Syntactic sugar for making mutable vectors
; (matrix (row ...) ...) instead of (vector (vector ...) ...)
(define-syntax-rule (matrix row ...)
  (vector row ...))
(define-syntax-rule (row item ...)
  (vector item ...))
    
;; Setters, getters, predicates

(define (matrix-set! m i j v)
  (vector-set! (vector-ref m i) j v))

(define (matrix-ref m i j)
  (vector-ref (vector-ref m i) j))

(define (matrix-size m)
  (values (vector-length m)
          (vector-length (vector-ref m 0))))

(define (matrix? m)
  (and (vector? m)
       (vector? (vector-ref m 0))))

;; basic iterator
(define (matrix-map f . ms)
  (apply vector-map 
         (lambda vs 
           (apply vector-map f vs))
         ms))

;;; Arithmetic operators
(define (matrix*vector m v [multiply *][add +])
  (vector-map
   (lambda (row)
     (for/fold 
         [(sum 0)] 
         [(product (vector-map multiply row v))]
       (add sum product)))
   m))

(define (matrix*matrix a1 a2 [multiply *][add +])
  (let-values [((m1 n1)(matrix-size a1))
               ((m2 n2)(matrix-size a2))]
    (if (= n1 m2)
        (build-matrix m1 n2 (lambda (r c)
                              (for/fold
                                  [(sum 0)]
                                [(i (in-range n1))]
                                (add sum (multiply (matrix-ref a1 r i)
                                                   (matrix-ref a2 i c))))))
        (error "Incompatibly sized matrices"))))

;;; Other operators
(define (transpose m)
  (let-values [((columns rows) (matrix-size m))]
    (build-matrix rows columns (lambda (i j)
                                 (matrix-ref m j i)))))