diff -r 566f4b2750e8 -r 1b5dc2468ce3 progs/compile_arr2.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/compile_arr2.scala	Mon Jan 27 10:11:44 2020 +0000
@@ -0,0 +1,238 @@
+// A Small Compiler for the WHILE Language
+//
+//  - includes arrays and a small parser for
+//    WHILE programs
+//
+//  - transpiles BF programs into WHILE programs
+//    and compiles and runs them
+//
+// Call with
+//
+// scala compiler_arr.scala
+
+
+
+// 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 ArrayDef(s: String, n: Int) 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             // var := exp
+case class AssignA(s: String, a1: AExp, a2: AExp) extends Stmt // arr[exp1] := exp2
+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
+case class Ref(s: String, a: 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 static write(I)V 
+    .limit locals 1 
+    .limit stack 2 
+    getstatic java/lang/System/out Ljava/io/PrintStream; 
+    iload 0
+    i2c       ; Int => Char
+    invokevirtual java/io/PrintStream/print(C)V   ; println(I)V => print(C)V    
+    return 
+.end method
+
+.method public static main([Ljava/lang/String;)V
+   .limit locals 200
+   .limit stack 200
+
+; COMPILED CODE STARTS   
+
+"""
+
+val ending = """
+; COMPILED CODE ENDS
+   return
+
+.end method
+"""
+
+
+
+
+// for generating new labels
+var counter = -1
+
+def Fresh(x: String) = {
+  counter += 1
+  x ++ "_" ++ counter.toString()
+}
+
+// environments and instructions
+type Env = Map[String, Int]
+
+// convenient string interpolations 
+// for instructions and labels
+import scala.language.implicitConversions
+import scala.language.reflectiveCalls
+
+implicit def sring_inters(sc: StringContext) = new {
+    def i(args: Any*): String = "   " ++ sc.s(args:_*) ++ "\n"
+    def l(args: Any*): String = sc.s(args:_*) ++ ":\n"
+}
+
+def compile_op(op: String) = op match {
+  case "+" => i"iadd"
+  case "-" => i"isub"
+  case "*" => i"imul"
+}
+
+// arithmetic expression compilation
+def compile_aexp(a: AExp, env : Env) : String = a match {
+  case Num(i) => i"ldc $i"
+  case Var(s) => i"iload ${env(s)}"
+  case Aop(op, a1, a2) => 
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ compile_op(op)
+  case Ref(s, a) =>
+    i"aload ${env(s)}" ++ compile_aexp(a, env) ++  i"iaload"
+}
+
+def compile_bop(op: String, jmp: String) = op match {
+  case "==" => i"if_icmpne $jmp"
+  case "!=" => i"if_icmpeq $jmp"
+  case "<"  => i"if_icmpge $jmp"
+}
+
+// boolean expression compilation
+def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match {
+  case True => ""
+  case False => i"goto $jmp"
+  case Bop(op, a1, a2) => 
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ compile_bop(op, jmp)
+}
+
+// statement compilation
+def compile_stmt(s: Stmt, env: Env) : (String, Env) = s match {
+  case Skip => ("", env)
+  case Assign(x, a) => {
+     val index = env.getOrElse(x, env.keys.size)
+    (compile_aexp(a, env) ++ i"istore $index \t\t; $x", 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 ++
+     i"goto $if_end" ++
+     l"$if_else" ++
+     instrs2 ++
+     l"$if_end", env2)
+  }
+  case While(b, bl) => {
+    val loop_begin = Fresh("Loop_begin")
+    val loop_end = Fresh("Loop_end")
+    val (instrs1, env1) = compile_block(bl, env)
+    (l"$loop_begin" ++
+     compile_bexp(b, env, loop_end) ++
+     instrs1 ++
+     i"goto $loop_begin" ++
+     l"$loop_end", env1)
+  }
+  case Write(x) => 
+    (i"iload ${env(x)} \t\t; $x" ++ 
+     i"invokestatic XXX/XXX/write(I)V", env)
+  case Read(x) => {
+    val index = env.getOrElse(x, env.keys.size) 
+    (i"invokestatic XXX/XXX/read()I" ++ 
+     i"istore $index \t\t; $x", env + (x -> index))
+  }
+  case ArrayDef(s: String, n: Int) => {
+    val index = if (env.isDefinedAt(s)) throw new Exception("array def error") else 
+                    env.keys.size
+    (i"ldc $n" ++
+     i"newarray int" ++
+     i"astore $index", env + (s -> index))
+  }
+  case AssignA(s, a1, a2) => {
+    val index = if (env.isDefinedAt(s)) env(s) else 
+                    throw new Exception("array not defined")
+    (i"aload ${env(s)}" ++
+     compile_aexp(a1, env) ++
+     compile_aexp(a2, env) ++
+     i"iastore", env)
+  } 
+}
+
+// compilation of a block (i.e. list of statements)
+def compile_block(bl: Block, env: Env) : (String, Env) = bl match {
+  case 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())._1
+  (beginning ++ instructions ++ ending).replaceAllLiterally("XXX", class_name)
+}
+
+
+import scala.util._
+import scala.sys.process._
+
+def time_needed[T](i: Int, code: => T) = {
+  val start = System.nanoTime()
+  for (j <- 2 to i) code
+  val result = code
+  val end = System.nanoTime()
+  ((end - start) / (i * 1.0e9), result)
+}
+
+def compile_to_file(bl: Block, class_name: String) : Unit = 
+  Using(new java.io.FileWriter(class_name + ".j")) {
+    _.write(compile(bl, class_name))
+  }
+
+def compile_and_run(bl: Block, class_name: String) : Unit = {
+  println(s"Start compilation of $class_name")
+  compile_to_file(bl, class_name)
+  println("generated .j file")
+  (s"java -jar jvm/jasmin-2.4/jasmin.jar ${class_name}.j").!!
+  println("generated .class file ")
+  println("Time: " + time_needed(1, (s"java ${class_name}/${class_name}").!)._1)
+}
+
+
+val arr_test = 
+  List(ArrayDef("a", 10),               // new(a[10])
+       ArrayDef("b", 2),                // new(b[2])
+       AssignA("a", Num(0), Num(10)),   // a[0] := 10
+       Assign("x", Ref("a", Num(0))),   // x := a[0]
+       Write("x"),                      // write x
+       AssignA("b", Num(2), Num(5)),    // b[2] := 5
+       Assign("x", Ref("b", Num(1))),   // x := b[1]
+       Write("x"))                      // write x
+
+
+compile_and_run(arr_test, "a")
+