diff -r 3db4970ad0aa -r e33545bb2eba progs/compile_arr.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/compile_arr.scala	Tue Nov 27 00:45:26 2018 +0000
@@ -0,0 +1,261 @@
+// A Small Compiler for the WHILE Language
+// (it does not use a parser and lexer)
+
+// the abstract syntax trees
+abstract class Stmt
+abstract class AExp
+abstract class BExp 
+type Block = List[Stmt]
+
+// statements
+case object Skip extends Stmt
+case class If(a: BExp, bl1: Block, bl2: Block) extends Stmt
+case class While(b: BExp, bl: Block) extends Stmt
+case class Assign(s: String, a: AExp) extends Stmt
+case class Write(s: String) extends Stmt
+case class Read(s: String) extends Stmt
+
+// arithmetic expressions
+case class Var(s: String) extends AExp
+case class Num(i: Int) extends AExp
+case class Aop(o: String, a1: AExp, a2: AExp) extends AExp
+
+// boolean expressions
+case object True extends BExp
+case object False extends BExp
+case class Bop(o: String, a1: AExp, a2: AExp) extends BExp
+
+
+// compiler headers needed for the JVM
+// (contains an init method, as well as methods for read and write)
+val beginning = """
+.class public XXX.XXX
+.super java/lang/Object
+
+.method public <init>()V
+   aload_0
+   invokenonvirtual java/lang/Object/<init>()V
+   return
+.end method
+
+.method public static write(I)V 
+    .limit locals 1 
+    .limit stack 2 
+    getstatic java/lang/System/out Ljava/io/PrintStream; 
+    iload 0
+    invokevirtual java/io/PrintStream/println(I)V 
+    return 
+.end method
+
+.method public static read()I 
+    .limit locals 10 
+    .limit stack 10
+
+    ldc 0 
+    istore 1  ; this will hold our final integer 
+Label1: 
+    getstatic java/lang/System/in Ljava/io/InputStream; 
+    invokevirtual java/io/InputStream/read()I 
+    istore 2 
+    iload 2 
+    ldc 10   ; the newline delimiter 
+    isub 
+    ifeq Label2 
+    iload 2 
+    ldc 32   ; the space delimiter 
+    isub 
+    ifeq Label2
+
+    iload 2 
+    ldc 48   ; we have our digit in ASCII, have to subtract it from 48 
+    isub 
+    ldc 10 
+    iload 1 
+    imul 
+    iadd 
+    istore 1 
+    goto Label1 
+Label2: 
+    ;when we come here we have our integer computed in local variable 1 
+    iload 1 
+    ireturn 
+.end method
+
+.method public static main([Ljava/lang/String;)V
+   .limit locals 200
+   .limit stack 200
+
+"""
+
+val ending = """
+
+   return
+
+.end method
+"""
+
+println("Start compilation")
+
+
+// for generating new labels
+var counter = -1
+
+def Fresh(x: String) = {
+  counter += 1
+  x ++ "_" ++ counter.toString()
+}
+
+// environments and instructions
+type Env = Map[String, String]
+type Instrs = List[String]
+
+// arithmetic expression compilation
+def compile_aexp(a: AExp, env : Env) : Instrs = a match {
+  case Num(i) => List("ldc " + i.toString + "\n")
+  case Var(s) => List("iload " + env(s) + "\n")
+  case Aop("+", a1, a2) => 
+    compile_aexp(a1, env) ++ 
+    compile_aexp(a2, env) ++ List("iadd\n")
+  case Aop("-", a1, a2) => 
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ List("isub\n")
+  case Aop("*", a1, a2) => 
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ List("imul\n")
+}
+
+// boolean expression compilation
+def compile_bexp(b: BExp, env : Env, jmp: String) : Instrs = b match {
+  case True => Nil
+  case False => List("goto " + jmp + "\n")
+  case Bop("=", a1, a2) => 
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ 
+    List("if_icmpne " + jmp + "\n")
+  case Bop("!=", a1, a2) => 
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ 
+    List("if_icmpeq " + jmp + "\n")
+  case Bop("<", a1, a2) => 
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ 
+    List("if_icmpge " + jmp + "\n")
+}
+
+// statement compilation
+def compile_stmt(s: Stmt, env: Env) : (Instrs, Env) = s match {
+  case Skip => (Nil, env)
+  case Assign(x, a) => {
+    val index = if (env.isDefinedAt(x)) env(x) else 
+                    env.keys.size.toString
+    (compile_aexp(a, env) ++ 
+     List("istore " + index + "\n"), env + (x -> index))
+  } 
+  case If(b, bl1, bl2) => {
+    val if_else = Fresh("If_else")
+    val if_end = Fresh("If_end")
+    val (instrs1, env1) = compile_block(bl1, env)
+    val (instrs2, env2) = compile_block(bl2, env1)
+    (compile_bexp(b, env, if_else) ++
+     instrs1 ++
+     List("goto " + if_end + "\n") ++
+     List("\n" + if_else + ":\n\n") ++
+     instrs2 ++
+     List("\n" + if_end + ":\n\n"), env2)
+  }
+  case While(b, bl) => {
+    val loop_begin = Fresh("Loop_begin")
+    val loop_end = Fresh("Loop_end")
+    val (instrs1, env1) = compile_block(bl, env)
+    (List("\n" + loop_begin + ":\n\n") ++
+     compile_bexp(b, env, loop_end) ++
+     instrs1 ++
+     List("goto " + loop_begin + "\n") ++
+     List("\n" + loop_end + ":\n\n"), env1)
+  }
+  case Write(x) => 
+    (List("iload " + env(x) + "\n" + 
+           "invokestatic XXX/XXX/write(I)V\n"), env)
+  case Read(x) => {
+    val index = if (env.isDefinedAt(x)) env(x) else 
+                    env.keys.size.toString
+    (List("invokestatic XXX/XXX/read()I\n" + 
+          "istore " + index + "\n"), env + (x -> index))
+  }
+}
+
+// compilation of a block (i.e. list of instructions)
+def compile_block(bl: Block, env: Env) : (Instrs, Env) = bl match {
+  case Nil => (Nil, env)
+  case s::bl => {
+    val (instrs1, env1) = compile_stmt(s, env)
+    val (instrs2, env2) = compile_block(bl, env1)
+    (instrs1 ++ instrs2, env2)
+  }
+}
+
+// main compilation function for blocks
+def compile(bl: Block, class_name: String) : String = {
+  val instructions = compile_block(bl, Map.empty)._1
+  (beginning ++ instructions.mkString ++ ending).replaceAllLiterally("XXX", class_name)
+}
+
+
+// compiling and running files
+//
+// JVM files can be assembled with 
+//
+//    java -jar jvm/jasmin-2.4/jasmin.jar fib.j
+//
+// and started with
+//
+//    java fib/fib
+
+
+
+import scala.util._
+import scala.sys.process._
+import scala.io
+
+def compile_tofile(bl: Block, class_name: String) = {
+  val output = compile(bl, class_name)
+  val fw = new java.io.FileWriter(class_name + ".j") 
+  fw.write(output) 
+  fw.close()
+}
+
+def compile_all(bl: Block, class_name: String) : Unit = {
+  compile_tofile(bl, class_name)
+  println("compiled ")
+  val test = ("java -jar jvm/jasmin-2.4/jasmin.jar " + class_name + ".j").!!
+  println("assembled ")
+}
+
+def time_needed[T](i: Int, code: => T) = {
+  val start = System.nanoTime()
+  for (j <- 1 to i) code
+  val end = System.nanoTime()
+  (end - start)/(i * 1.0e9)
+}
+
+
+def compile_run(bl: Block, class_name: String) : Unit = {
+  println("Start compilation")
+  compile_all(bl, class_name)
+  println("Time: " + time_needed(1, ("java " + class_name + "/" + class_name).!))
+}
+
+
+// Fibonacci numbers as a test-case
+val fib_test = 
+  List(Assign("n", Num(10)),            //  n := 10;                     
+       Assign("minus1",Num(0)),         //  minus1 := 0;
+       Assign("minus2",Num(1)),         //  minus2 := 1;
+       Assign("temp",Num(0)),           //  temp := 0;
+       While(Bop("<",Num(0),Var("n")),  //  while n > 0 do  {
+          List(Assign("temp",Var("minus2")),    //  temp := minus2;
+               Assign("minus2",Aop("+",Var("minus1"),Var("minus2"))), 
+                                        //  minus2 := minus1 + minus2;
+               Assign("minus1",Var("temp")), //  minus1 := temp;
+               Assign("n",Aop("-",Var("n"),Num(1))))), //  n := n - 1 };
+       Write("minus1"))                 //  write minus1
+
+
+compile_run(fib_test, "fib")
+
+