--- a/progs/compile.scala	Sun Jul 28 01:00:41 2019 +0100
+++ b/progs/compile.scala	Sun Jul 28 14:24:46 2019 +0100
@@ -1,6 +1,7 @@
 // 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
@@ -85,16 +86,18 @@
    .limit locals 200
    .limit stack 200
 
+; COMPILED CODE STARTS
+
 """
 
 val ending = """
-
+; COMPILED CODE ENDS
    return
 
 .end method
 """
 
-println("Start compilation")
+// Compiler functions
 
 
 // for generating new labels
@@ -105,46 +108,51 @@
   x ++ "_" ++ counter.toString()
 }
 
-// environments and instructions
+// 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"
+}
+
+
+// environments 
 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")
+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("+", a1, a2) => 
-    compile_aexp(a1, env) ++ 
-    compile_aexp(a2, env) ++ List("iadd\n")
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"iadd"
   case Aop("-", a1, a2) => 
-    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ List("isub\n")
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"isub"
   case Aop("*", a1, a2) => 
-    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ List("imul\n")
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"imul"
 }
 
 // boolean expression compilation
-def compile_bexp(b: BExp, env : Env, jmp: String) : Instrs = b match {
-  case True => Nil
-  case False => List("goto " + jmp + "\n")
+def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match {
+  case True => ""
+  case False => i"goto $jmp"
   case Bop("=", a1, a2) => 
-    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ 
-    List("if_icmpne " + jmp + "\n")
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"if_icmpne $jmp"
   case Bop("!=", a1, a2) => 
-    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ 
-    List("if_icmpeq " + jmp + "\n")
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"if_icmpeq $jmp"
   case Bop("<", a1, a2) => 
-    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ 
-    List("if_icmpge " + jmp + "\n")
+    compile_aexp(a1, env) ++ compile_aexp(a2, env) ++ i"if_icmpge $jmp"
 }
 
 // statement compilation
-def compile_stmt(s: Stmt, env: Env) : (Instrs, Env) = s match {
-  case Skip => (Nil, env)
+def compile_stmt(s: Stmt, env: Env) : (String, Env) = s match {
+  case Skip => ("", 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))
+    (compile_aexp(a, env) ++ i"istore $index", env + (x -> index))
   } 
   case If(b, bl1, bl2) => {
     val if_else = Fresh("If_else")
@@ -153,35 +161,35 @@
     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") ++
+     i"goto $if_end" ++
+     l"$if_else" ++
      instrs2 ++
-     List("\n" + if_end + ":\n\n"), env2)
+     l"$if_end", env2)
   }
   case While(b, bl) => {
     val loop_begin = Fresh("Loop_begin")
     val loop_end = Fresh("Loop_end")
     val (instrs1, env1) = compile_block(bl, env)
-    (List("\n" + loop_begin + ":\n\n") ++
+    (l"$loop_begin" ++
      compile_bexp(b, env, loop_end) ++
      instrs1 ++
-     List("goto " + loop_begin + "\n") ++
-     List("\n" + loop_end + ":\n\n"), env1)
+     i"goto $loop_begin" ++
+     l"$loop_end", env1)
   }
   case Write(x) => 
-    (List("iload " + env(x) + "\n" + 
-           "invokestatic XXX/XXX/write(I)V\n"), env)
+    (i"iload ${env(x)}" ++ 
+     i"invokestatic XXX/XXX/write(I)V", 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))
+    (i"invokestatic XXX/XXX/read()I" ++ 
+     i"istore $index", 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)
+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)
@@ -237,6 +245,7 @@
 def compile_run(bl: Block, class_name: String) : Unit = {
   println("Start compilation")
   compile_all(bl, class_name)
+  println("running")
   println("Time: " + time_needed(1, ("java " + class_name + "/" + class_name).!))
 }