#/***********************************************************
#    fracint.rb -- フラクタル補間
#***********************************************************/
require "window.rb"

left = 0; bottom = 0; right = 100; top = 100
x = [0, 30, 60, 100]; y = [0, 50, 40, 10]  # 各点の座標 

N = x.size - 1

a = []; c = []; d = []; e = []; f = []

# アフィン変換を求める 
q = x[N] - x[0]
for i in 0...N
    printf("d[%d] = ", i);  d[i] = gets.to_f
    a[i] = (x[i+1] - x[i]) / q.to_f
    e[i] = (x[N] * x[i] - x[0] * x[i+1]) / q.to_f
    c[i] = (y[i+1] - y[i] - d[i] * (y[N] - y[0])) / q.to_f
    f[i] = (x[N] * y[i] - x[0] * y[i+1] -\
            d[i] * (x[N] * y[0] - x[0] * y[N])) / q.to_f
end
# アトラクタをプロットする 
gr_on(true)
gr_window(left, bottom, right, top, 0, 0)
gr_plot_start
p = x[0];  q = y[0]
for i in 0...5000
    j = (N * rand()).to_i
    q = c[j] * p + d[j] * q + f[j]
    p = a[j] * p            + e[j]
    gr_wdot(p, q)
end
gr_plot_end
gr_off

exit 0