diff -r 484b74bc057e -r 3a5a7908517f progs/compile_arr.scala
--- a/progs/compile_arr.scala	Wed Nov 20 17:10:03 2019 +0000
+++ b/progs/compile_arr.scala	Thu Nov 21 00:49:21 2019 +0000
@@ -445,6 +445,13 @@
   prog.toList.map(instr).mkString
 
 
+// the mandelbrot.bf program is so large that
+// it does not fit into the limitations of what the
+// JVM imposes on methods.
+//
+// below it just about fits by optimising [-] loops
+// and combining instructions
+
 def splice(cs: List[Char], acc: List[(Char, Int)]) : List[(Char, Int)] = (cs, acc) match {
   case (Nil, acc) => acc
   case (c :: cs, Nil) => splice(cs, List((c, 1)))
@@ -456,26 +463,24 @@
 def spl(s: String) = splice(s.toList, Nil).reverse
 
 def instr2(c: Char, n: Int) : String = c match {
-  case '>' => "ptr := ptr + " + n.toString + ";"
-  case '<' => "ptr := ptr - " + n.toString + ";"
-  case '+' => "field[ptr] := field[ptr] + " + n.toString + ";"
-  case '-' => "field[ptr] := field[ptr] - " + n.toString + ";"
-  case '.' => "x := field[ptr]; write x;" //* n
-  //case ',' => "*ptr = getchar();\n" * n
+  case '>' => s"ptr := ptr + $n;"
+  case '<' => s"ptr := ptr - $n;"
+  case '0' => s"field[ptr] := 0;"
+  case '+' => s"field[ptr] := field[ptr] + $n;"
+  case '-' => s"field[ptr] := field[ptr] - $n;"
+  case '.' => s"x := field[ptr]; write x;" 
   case '['  => "while (field[ptr] != 0) do {" * n 
   case ']'  => "skip};" * n
   case _ => ""
 }
 
 def instrs2(prog: String) : String =
-  spl(prog).map{ case (c, n) => instr2(c, n) }.mkString
-
+  spl(prog.replaceAll("""\[-\]""", "0")).map{ case (c, n) => instr2(c, n) }.mkString
 
 def bf_str(prog: String) : String = {
   "\n" ++
-  //"new field[30000];\n" ++
   "ptr := 15000;" ++
-  instrs(prog) ++
+  instrs2(prog) ++
   "skip"
 }
 
@@ -523,7 +528,6 @@
 
 bf_run(bf2, "fibs")
 
-/*
 
 
 bf_run("""      A mandelbrot set fractal viewer in brainf*** written by Erik Bosman
@@ -672,4 +676,4 @@
 +[-[->>>>>>>>>+<<<<<<<<<]>>>>>>>>>]>>>>>->>>>>>>>>>>>>>>>>>>>>>>>>>>-<<<<<<[<<<<
 <<<<<]]>>>]""", "mand")
 
-*/
+