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customize default return value of matrix-get when peeking outside

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Daniel Borges
2021-12-11 10:49:04 +01:00
parent a1266ca648
commit f0d18d31ce
2 changed files with 22 additions and 13 deletions
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12
09-smoke-basin/code.scm
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@@ -17,10 +17,10 @@
(lambda (y line)
(vector-for-each
(lambda (x altitude)
(let [(left (matrix-get heightmap (- x 1) y))
(right (matrix-get heightmap (+ x 1) y))
(up (matrix-get heightmap x (- y 1)))
(down (matrix-get heightmap x (+ y 1)))]
(let [(left (matrix-get heightmap (- x 1) y 9))
(right (matrix-get heightmap (+ x 1) y 9))
(up (matrix-get heightmap x (- y 1) 9))
(down (matrix-get heightmap x (+ y 1) 9))]
(when (and (< altitude left)
(< altitude right)
(< altitude up)
@@ -49,7 +49,7 @@
(let [(ofs (offset x y))]
(when (= (vector-ref visited ofs) 0)
(vector-set! visited ofs 1)
(when (< (matrix-get heightmap x y) 9)
(when (< (matrix-get heightmap x y 9) 9)
(closure x y)
(when (> x 0) (flood-fill (- x 1) y))
(when (< x width-1) (flood-fill (+ x 1) y))
@@ -103,7 +103,7 @@
(let y-loop [(y 0)]
(let x-loop [(x 0)]
(let [(ofs (offset x y))
(gray-level (* (matrix-get heightmap x y) 20))]
(gray-level (* (matrix-get heightmap x y 9) 20))]
; red channel
(vector-set! data ofs gray-level)
; green channel

23
common.scm
View File

@@ -13,19 +13,28 @@
(- (char->integer c) 48)) ; 48 is ASCII's number zero
(define-record-type matrix (fields width height data))
(define (matrix-get matrix x y)
(if (or (< x 0)
(< y 0)
(>= x (matrix-width matrix))
(>= y (matrix-height matrix)))
9
(vector-ref (vector-ref (matrix-data matrix) y) x)))
(define (matrix-from-data data)
(make-matrix
(vector-length (vector-ref data 0))
(vector-length data)
data))
(define (matrix-get matrix x y default)
(if (or (< x 0)
(< y 0)
(>= x (matrix-width matrix))
(>= y (matrix-height matrix)))
default
(vector-ref (vector-ref (matrix-data matrix) y) x)))
(define (matrix-set! matrix x y value)
(when (and (>= x 0)
(>= y 0)
(< x (matrix-width matrix))
(< y (matrix-height matrix)))
(vector-set! (vector-ref (matrix-data matrix) y) x value)))
; parse 0-9 numerical data from file and return a matrix
(define (load-matrix file)
(let y-loop [(heightmap '())]