(* Kurver.sml * Copyright 1998 Peter Sestoft.  
   Må kopieres og modificeres jvfr. GNU General Public License *)

fun kurver () = 
    let val gen = Random.newgen ()
	val ser = Random.range (4, 8) gen
	val n   = Random.range (20, 30) gen
	fun mkseries trend = 
	    List.tabulate(n, fn i => trend i * (1.0 - 0.3 * Random.random gen))
	fun trend1 i = real i / 2.0 + 2.0;
	fun trend2 i = real (n-i) / 3.0 + 2.0;
	fun trend3 i = Math.ln (real (i+1)) * 4.0 + 2.0
	fun trend4 i = real (abs (n div 2 - i)) + 2.0
	val trendlist = List.take([trend1, trend2, trend3, trend4, 
				   trend1, trend2, trend3, trend4], ser)
	val trends = Array.fromList trendlist

	fun permutearray arr = 
	    let val len = Array.length arr
		fun swaprandom (i, a) = 
		    let val j = Random.range (0, len) gen 
		    in
			Array.update(arr, i, Array.sub(arr, j));
			Array.update(arr, j, a)
		    end
	    in Array.appi swaprandom (arr, 0, NONE) end

	val _ = permutearray trends
	val data = Array.foldr (fn (t, res) => mkseries t :: res) [] trends

	fun loop 0 tilnu = tilnu
	  | loop i res = 
	    let val (_, _, ordsek, ok) = 
		Substant.vaelg (SOME (Basis.ubs, Basis.flt))
	    in 
		if ok andalso List.all (fn ord1 => ord1 <> ordsek) res then 
		    loop (i-1) (ordsek :: res)
		else loop i res
	    end
	val tekster = 
	    List.map (Format.flatten o Format.begyndelse) (loop ser [])
    in 
	Gdimage.stdoutGif (Graphs.accugraph (550, 220) data tekster)
    end

val _ = kurver ();