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「Mandelbrot (マンデルブロート) 集合」(2010/11/02 (火) 21:39:49) の最新版変更点

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#asciiart(blockquote){
/***********************************************************
	mandel.c -- Mandelbrot (マンデルブロート) 集合
***********************************************************/
#N88BASIC

Const M = 1000
Const XMAX = 640
Const YMAX = 400
Sub main()
	Dim i As Long, j As Long, imax As Long, jmax As Long
	Dim maxiter As Long, count As Long

	Dim xmin, xmax, ymin, ymax, x, y, a, b, a2, b2, dx, dy

	Dim color[M] As Long


	Input "xmin = ";xmin
	Input "xmax = ";xmax
	Input "ymin = ";ymin
	Input "ymax = ";ymax
	Input "maxiter = ";maxiter

	dx = xmax - xmin
	dy = ymax - ymin

	If dx <= 0 or dy <= 0 or maxiter <= 0 or maxiter > M Then
		End
	End If

	If dx * YMAX > dy * XMAX Then
		imax = XMAX:  jmax = (XMAX * dy / dx + 0.5)
	Else
		imax = (YMAX * dx / dy + 0.5) : jmax = YMAX
	End If

	dx = dx / imax
	dy = dy / jmax
	color[0] = 0
	j = 7

	For i = maxiter To 1 Step -1
		color[i] = j
		If j > 1 Then j=j-1
	Next

	For i = 0 To imax
		x = xmin + i * dx
		For j = 0 To jmax
			y = ymax - j * dy : a = x : b = y
			a2 = a * a :  b2 = b * b :  count = maxiter
			While (a2 + b2 <= 4 And count)
				b = 2 * a * b - y :  a = a2 - b2 - x
				a2 = a * a :  b2 = b * b : count = count - 1
			Wend
			Pset(i, j), color[count]
		Next
	Next
End Sub

main()
}