updatd
authorChristian Urban <christian dot urban at kcl dot ac dot uk>
Mon, 20 Jul 2020 10:06:43 +0100
changeset 735 fc2e3609d5e5
parent 734 5d860ff01938
child 736 d3e477fe6c66
updatd
handouts/graphs.pdf
handouts/ho01.pdf
handouts/ho02.pdf
handouts/ho03.pdf
handouts/ho04.pdf
handouts/ho05.pdf
handouts/ho06.pdf
handouts/ho07.pdf
handouts/ho08.pdf
handouts/ho09.pdf
handouts/ho10.pdf
handouts/notation.pdf
handouts/scala-ho.pdf
hws/hw01.pdf
hws/hw02.pdf
hws/hw03.pdf
hws/hw04.pdf
hws/hw05.pdf
hws/hw06.pdf
hws/hw07.pdf
hws/hw08.pdf
hws/hw09.pdf
hws/proof.pdf
progs/fun/defs.fun
progs/fun/fact.fun
progs/fun/fun-bare.scala
progs/fun/fun-orig.scala
progs/fun/fun.sc
progs/fun/fun.scala
Binary file handouts/graphs.pdf has changed
Binary file handouts/ho01.pdf has changed
Binary file handouts/ho02.pdf has changed
Binary file handouts/ho03.pdf has changed
Binary file handouts/ho04.pdf has changed
Binary file handouts/ho05.pdf has changed
Binary file handouts/ho06.pdf has changed
Binary file handouts/ho07.pdf has changed
Binary file handouts/ho08.pdf has changed
Binary file handouts/ho09.pdf has changed
Binary file handouts/ho10.pdf has changed
Binary file handouts/notation.pdf has changed
Binary file handouts/scala-ho.pdf has changed
Binary file hws/hw01.pdf has changed
Binary file hws/hw02.pdf has changed
Binary file hws/hw03.pdf has changed
Binary file hws/hw04.pdf has changed
Binary file hws/hw05.pdf has changed
Binary file hws/hw06.pdf has changed
Binary file hws/hw07.pdf has changed
Binary file hws/hw08.pdf has changed
Binary file hws/hw09.pdf has changed
Binary file hws/proof.pdf has changed
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/fun/defs.fun	Mon Jul 20 10:06:43 2020 +0100
@@ -0,0 +1,85 @@
+
+def zero(x) = 0;
+
+def suc(x) = x + 1;
+
+def pred(x) =
+  if x == 0 then x else x - 1;
+
+def add(x, y) =
+  if x == 0 then y else suc(add(x - 1, y));
+
+def mult(x, y) =
+  if x == 0 then 0 else add(y, mult(x - 1, y));
+
+def pow(x, y) =
+  if y == 0 then 1 else mult(x, pow(x, y - 1));
+
+def fib(n) = if n == 0 then 0 
+             else if n == 1 then 1 
+             else fib(n - 1) + fib(n - 2);
+
+def fact(n) =
+  if n == 0 then 1 else n * fact(n - 1);
+
+def ack(m, n) = if m == 0 then n + 1
+                else if n == 0 then ack(m - 1, 1)
+                else ack(m - 1, ack(m, n - 1));
+
+def stack_test(x) = x + 1 + 2 + 3 + 4 + 5;
+
+def div(x, y) = x / y;   //integer division
+
+def rem(x, y) = x % y;   //remainder
+
+def gcd(a, b) =
+  if b == 0 then a else gcd(b, a % b);
+
+def is_prime_aux(n, i) = 
+  if n % i == 0 then 0
+  else if (i * i) <= n then is_prime_aux(n, i + 1)  
+  else 1;
+
+def is_prime(n) = if n == 2 then 1 else is_prime_aux(n, 2);
+
+def primes(n) = 
+  if n == 0 then 0
+  else if is_prime(n) == 1 then (write n; primes(n - 1)) 
+  else primes(n - 1);
+
+def is_collatz(n) =
+  if n == 1 then 1
+  else if n % 2 == 0 then is_collatz(n / 2)
+  else is_collatz(3 * n + 1);  
+
+def collatz_aux(n, i) = 
+  if i > n then 0
+  else if is_collatz(i) == 1 then (write i; collatz_aux(n, i + 1)) 
+  else collatz_aux(n, i + 1);
+
+def collatz(n) = collatz_aux(n, 1);
+
+def facT(n, acc) =
+  if n == 0 then acc else facT(n - 1, n * acc);
+
+
+//zero(3)
+//suc(8)
+//pred(7)
+//write(add(3, 4))
+//mult(4,5)
+//pow(2, 3)
+//fib(20)
+//(write(fact(5)) ; fact(6))
+//(write(1) ; 2)
+//write(ack(3, 12))   // for tail-rec test
+//stack_test(0)
+//(write (div(11, 3)); rem(11, 3))
+//gcd(54, 24)
+//is_prime(2)
+primes(1000)
+//primes(1000000)
+//collatz(4000)
+//collatz(5000)
+//facT(6, 1)
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/fun/fact.fun	Mon Jul 20 10:06:43 2020 +0100
@@ -0,0 +1,15 @@
+def fact(n) =
+  (if n == 0 then 1 else n * fact(n - 1));
+
+def facT(n, acc) =
+  if n == 0 then acc else facT(n - 1, n * acc);
+
+def facTi(n) = facT(n, 1);
+
+//fact(10)
+//facTi(10)
+
+write(facTi(6))
+
+// a simple factorial program
+// (including a tail recursive version)
--- a/progs/fun/fun-bare.scala	Sat Jul 04 22:12:18 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,187 +0,0 @@
-// A Small Compiler for a Simple Functional Language
-// (it does not include a parser and lexer)
-
-// abstract syntax trees
-abstract class Exp
-abstract class BExp 
-abstract class Decl
-
-// functions and declarations
-case class Def(name: String, args: List[String], body: Exp) extends Decl
-case class Main(e: Exp) extends Decl
-
-// expressions
-case class Call(name: String, args: List[Exp]) extends Exp
-case class If(a: BExp, e1: Exp, e2: Exp) extends Exp
-case class Write(e: Exp) extends Exp
-case class Var(s: String) extends Exp
-case class Num(i: Int) extends Exp
-case class Aop(o: String, a1: Exp, a2: Exp) extends Exp
-case class Sequ(e1: Exp, e2: Exp) extends Exp
-
-// boolean expressions
-case class Bop(o: String, a1: Exp, a2: Exp) extends BExp
-
-// calculating the maximal needed stack size
-def max_stack_exp(e: Exp): Int = e match {
-  case Call(_, args) => args.map(max_stack_exp).sum
-  case If(a, e1, e2) => max_stack_bexp(a) + (List(max_stack_exp(e1), max_stack_exp(e2)).max)
-  case Write(e) => max_stack_exp(e) + 1
-  case Var(_) => 1
-  case Num(_) => 1
-  case Aop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
-  case Sequ(e1, e2) => List(max_stack_exp(e1), max_stack_exp(e2)).max
-}
-def max_stack_bexp(e: BExp): Int = e match {
-  case Bop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
-}
-
-// compiler - built-in functions 
-// copied from http://www.ceng.metu.edu.tr/courses/ceng444/link/jvm-cpm.html
-//
-
-val library = """
-.class public XXX.XXX
-.super java/lang/Object
-
-.method public static write(I)V 
-        .limit locals 5 
-        .limit stack 5 
-        iload 0 
-        getstatic java/lang/System/out Ljava/io/PrintStream; 
-        swap 
-        invokevirtual java/io/PrintStream/println(I)V 
-        return 
-.end method
-
-"""
-
-// for generating new labels
-var counter = -1
-
-def Fresh(x: String) = {
-  counter += 1
-  x ++ "_" ++ counter.toString()
-}
-
-// convenient string interpolations for
-// generating instructions, labels etc
-import scala.language.implicitConversions
-import scala.language.reflectiveCalls
-
-// convenience for code-generation (string interpolations)
-implicit def sring_inters(sc: StringContext) = new {
-  def i(args: Any*): String = "   " ++ sc.s(args:_*) ++ "\n"  // instructions
-  def l(args: Any*): String = sc.s(args:_*) ++ ":\n"          // labels
-  def m(args: Any*): String = sc.s(args:_*) ++ "\n"           // methods
-}
-
-// variable / index environments
-type Env = Map[String, Int]
-
-// compile expressions
-def compile_exp(a: Exp, env : Env) : String = a match {
-  case Num(i) => i"ldc $i"
-  case Var(s) => i"iload ${env(s)}"
-  case Aop("+", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"iadd"
-  case Aop("-", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"isub"
-  case Aop("*", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"imul"
-  case Aop("/", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"idiv"
-  case Aop("%", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"irem"
-  case If(b, a1, a2) => {
-    val if_else = Fresh("If_else")
-    val if_end = Fresh("If_end")
-    compile_bexp(b, env, if_else) ++
-    compile_exp(a1, env) ++
-    i"goto $if_end" ++
-    l"$if_else" ++
-    compile_exp(a2, env) ++
-    l"$if_end"
-  }
-  case Call(name, args) => {
-    val is = "I" * args.length
-    args.map(a => compile_exp(a, env)).mkString ++
-    i"invokestatic XXX/XXX/$name($is)I"
-  }
-  case Sequ(a1, a2) => {
-    compile_exp(a1, env) ++ i"pop" ++ compile_exp(a2, env)
-  }
-  case Write(a1) => {
-    compile_exp(a1, env) ++
-    i"dup" ++
-    i"invokestatic XXX/XXX/write(I)V"
-  }
-}
-
-// compile boolean expressions
-def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match {
-  case Bop("==", a1, a2) => 
-    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpne $jmp"
-  case Bop("!=", a1, a2) => 
-    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpeq $jmp"
-  case Bop("<", a1, a2) => 
-    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpge $jmp"
-  case Bop("<=", a1, a2) => 
-    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpgt $jmp"
-}
-
-// compile functions and declarations
-def compile_decl(d: Decl) : String = d match {
-  case Def(name, args, a) => { 
-    val env = args.zipWithIndex.toMap
-    val is = "I" * args.length
-    m".method public static $name($is)I" ++
-    m".limit locals ${args.length.toString}" ++
-    m".limit stack ${1 + max_stack_exp(a)}" ++
-    l"${name}_Start" ++   
-    compile_exp(a, env) ++
-    i"ireturn" ++
-    m".end method\n"
-  }
-  case Main(a) => {
-    m".method public static main([Ljava/lang/String;)V" ++
-    m".limit locals 200" ++
-    m".limit stack 200" ++
-    compile_exp(a, Map()) ++
-    i"invokestatic XXX/XXX/write(I)V" ++
-    i"return" ++
-    m".end method\n"
-  }
-}
-
-// the main compilation function
-def compile(prog: List[Decl], class_name: String) : String = {
-  val instructions = prog.map(compile_decl).mkString
-  (library + instructions).replaceAllLiterally("XXX", class_name)
-}
-
-
-
-
-// An example program (factorials)
-//
-// def fact(n) = if n == 0 then 1 else n * fact(n - 1);
-// def facT(n, acc) = if n == 0 then acc else facT(n - 1, n * acc);
-// 
-// fact(10) ; facT(15, 1)
-// 
-
-
-val test_prog = 
-  List(Def("fact", List("n"),
-         If(Bop("==",Var("n"),Num(0)),
-            Num(1),
-            Aop("*",Var("n"),
-                    Call("fact",List(Aop("-",Var("n"),Num(1))))))),
-
-       Def("facT",List("n", "acc"),
-         If(Bop("==",Var("n"),Num(0)),
-            Var("acc"),
-            Call("facT",List(Aop("-",Var("n"),Num(1)), 
-                             Aop("*",Var("n"),Var("acc")))))),
-
-       Main(Sequ(Write(Call("fact",List(Num(10)))),
-                 Write(Call("facT",List(Num(10), Num(1)))))))
-
-// prints out the JVM instructions
-println(compile(test_prog, "fact"))
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/fun/fun-orig.scala	Mon Jul 20 10:06:43 2020 +0100
@@ -0,0 +1,210 @@
+// A Small Compiler for a Simple Functional Language
+// (includes an external lexer and parser)
+//
+// call with 
+//
+//     amm fun.scala fact
+//
+//     amm fun.scala defs
+//
+// this will generate a .j file and run the jasmin
+// assembler (installed at jvm/jasmin-2.4/jasmin.jar)
+// it runs the resulting JVM file twice for timing 
+// purposes.
+
+
+import java.io._  
+import scala.util._
+import scala.sys.process._
+
+// Abstract syntax trees for the Fun language
+abstract class Exp extends Serializable 
+abstract class BExp extends Serializable 
+abstract class Decl extends Serializable 
+
+case class Def(name: String, args: List[String], body: Exp) extends Decl
+case class Main(e: Exp) extends Decl
+
+case class Call(name: String, args: List[Exp]) extends Exp
+case class If(a: BExp, e1: Exp, e2: Exp) extends Exp
+case class Write(e: Exp) extends Exp
+case class Var(s: String) extends Exp
+case class Num(i: Int) extends Exp
+case class Aop(o: String, a1: Exp, a2: Exp) extends Exp
+case class Sequence(e1: Exp, e2: Exp) extends Exp
+case class Bop(o: String, a1: Exp, a2: Exp) extends BExp
+
+
+// compiler - built-in functions 
+// copied from http://www.ceng.metu.edu.tr/courses/ceng444/link/jvm-cpm.html
+//
+
+val library = """
+.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
+        invokevirtual java/io/PrintStream/println(I)V 
+        return 
+.end method
+
+"""
+
+// calculating the maximal needed stack size
+def max_stack_exp(e: Exp): Int = e match {
+  case Call(_, args) => args.map(max_stack_exp).sum
+  case If(a, e1, e2) => 
+    max_stack_bexp(a) + (List(max_stack_exp(e1), max_stack_exp(e2)).max)
+  case Write(e) => max_stack_exp(e) + 1
+  case Var(_) => 1
+  case Num(_) => 1
+  case Aop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
+  case Sequence(e1, e2) => List(max_stack_exp(e1), max_stack_exp(e2)).max
+}
+
+def max_stack_bexp(e: BExp): Int = e match {
+  case Bop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
+}
+
+
+// for generating new labels
+var counter = -1
+
+def Fresh(x: String) = {
+  counter += 1
+  x ++ "_" ++ counter.toString()
+}
+
+// convenient string interpolations 
+// for instructions, labels and methods
+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 m(args: Any*): String = sc.s(args:_*) ++ "\n"
+}
+
+
+type Env = Map[String, Int]
+
+// compile expressions
+def compile_exp(a: Exp, env : Env) : String = a match {
+  case Num(i) => i"ldc $i"
+  case Var(s) => i"iload ${env(s)}"
+  case Aop("+", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"iadd"
+  case Aop("-", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"isub"
+  case Aop("*", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"imul"
+  case Aop("/", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"idiv"
+  case Aop("%", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"irem"
+  case If(b, a1, a2) => {
+    val if_else = Fresh("If_else")
+    val if_end = Fresh("If_end")
+    compile_bexp(b, env, if_else) ++
+    compile_exp(a1, env) ++
+    i"goto $if_end" ++
+    l"$if_else" ++
+    compile_exp(a2, env) ++
+    l"$if_end"
+  }
+  case Call(name, args) => {
+    val is = "I" * args.length
+    args.map(a => compile_exp(a, env)).mkString ++
+    i"invokestatic XXX/XXX/$name($is)I"
+  }
+  case Sequence(a1, a2) => {
+    compile_exp(a1, env) ++ i"pop" ++ compile_exp(a2, env)
+  }
+  case Write(a1) => {
+    compile_exp(a1, env) ++
+    i"dup" ++
+    i"invokestatic XXX/XXX/write(I)V"
+  }
+}
+
+// compile boolean expressions
+def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match {
+  case Bop("==", a1, a2) => 
+    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpne $jmp"
+  case Bop("!=", a1, a2) => 
+    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpeq $jmp"
+  case Bop("<", a1, a2) => 
+    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpge $jmp"
+  case Bop("<=", a1, a2) => 
+    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpgt $jmp"
+}
+
+// compile function for declarations and main
+def compile_decl(d: Decl) : String = d match {
+  case Def(name, args, a) => { 
+    val env = args.zipWithIndex.toMap
+    val is = "I" * args.length
+    m".method public static $name($is)I" ++
+    m".limit locals ${args.length}" ++
+    m".limit stack ${1 + max_stack_exp(a)}" ++
+    l"${name}_Start" ++   
+    compile_exp(a, env) ++
+    i"ireturn" ++
+    m".end method\n"
+  }
+  case Main(a) => {
+    m".method public static main([Ljava/lang/String;)V" ++
+    m".limit locals 200" ++
+    m".limit stack 200" ++
+    compile_exp(a, Map()) ++
+    i"invokestatic XXX/XXX/write(I)V" ++
+    i"return" ++
+    m".end method\n"
+  }
+}
+
+// main compiler functions
+
+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 deserialise[T](fname: String) : Try[T] = {
+  import scala.util.Using
+  Using(new ObjectInputStream(new FileInputStream(fname))) {
+    in => in.readObject.asInstanceOf[T]
+  }
+}
+
+def compile(class_name: String) : String = {
+  val ast = deserialise[List[Decl]](class_name ++ ".prs").getOrElse(Nil) 
+  val instructions = ast.map(compile_decl).mkString
+  (library + instructions).replaceAllLiterally("XXX", class_name)
+}
+
+def compile_to_file(class_name: String) = {
+  val output = compile(class_name)
+  scala.tools.nsc.io.File(s"${class_name}.j").writeAll(output)
+}
+
+def compile_and_run(class_name: String) : Unit = {
+  compile_to_file(class_name)
+  (s"java -jar jvm/jasmin-2.4/jasmin.jar ${class_name}.j").!!
+  println("Time: " + time_needed(1, (s"java ${class_name}/${class_name}").!))
+}
+
+
+// some examples of .fun files
+//compile_to_file("fact")
+//compile_and_run("fact")
+//compile_and_run("defs")
+
+
+def main(args: Array[String]) : Unit = 
+   compile_and_run(args(0))
+
+
+}
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/fun/fun.sc	Mon Jul 20 10:06:43 2020 +0100
@@ -0,0 +1,201 @@
+// A Small Compiler for a Simple Functional Language
+// (it does not include a parser and lexer)
+//
+// call with
+//
+//    amm fun.sc
+//
+// this will print out the JVM instructions for two
+// factorial functions
+
+
+// abstract syntax trees
+abstract class Exp
+abstract class BExp 
+abstract class Decl
+
+// functions and declarations
+case class Def(name: String, args: List[String], body: Exp) extends Decl
+case class Main(e: Exp) extends Decl
+
+// expressions
+case class Call(name: String, args: List[Exp]) extends Exp
+case class If(a: BExp, e1: Exp, e2: Exp) extends Exp
+case class Write(e: Exp) extends Exp
+case class Var(s: String) extends Exp
+case class Num(i: Int) extends Exp
+case class Aop(o: String, a1: Exp, a2: Exp) extends Exp
+case class Sequ(e1: Exp, e2: Exp) extends Exp
+
+// boolean expressions
+case class Bop(o: String, a1: Exp, a2: Exp) extends BExp
+
+// calculating the maximal needed stack size
+def max_stack_exp(e: Exp): Int = e match {
+  case Call(_, args) => args.map(max_stack_exp).sum
+  case If(a, e1, e2) => 
+    max_stack_bexp(a) + (List(max_stack_exp(e1), max_stack_exp(e2)).max)
+  case Write(e) => max_stack_exp(e) + 1
+  case Var(_) => 1
+  case Num(_) => 1
+  case Aop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
+  case Sequ(e1, e2) => List(max_stack_exp(e1), max_stack_exp(e2)).max
+}
+def max_stack_bexp(e: BExp): Int = e match {
+  case Bop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
+}
+
+// compiler - built-in functions 
+// copied from http://www.ceng.metu.edu.tr/courses/ceng444/link/jvm-cpm.html
+//
+
+val library = """
+.class public XXX.XXX
+.super java/lang/Object
+
+.method public static write(I)V 
+        .limit locals 5 
+        .limit stack 5 
+        iload 0 
+        getstatic java/lang/System/out Ljava/io/PrintStream; 
+        swap 
+        invokevirtual java/io/PrintStream/println(I)V 
+        return 
+.end method
+
+"""
+
+// for generating new labels
+var counter = -1
+
+def Fresh(x: String) = {
+  counter += 1
+  x ++ "_" ++ counter.toString()
+}
+
+// convenient string interpolations for
+// generating instructions, labels etc
+import scala.language.implicitConversions
+import scala.language.reflectiveCalls
+
+// convenience for code-generation (string interpolations)
+implicit def sring_inters(sc: StringContext) = new {
+  def i(args: Any*): String = "   " ++ sc.s(args:_*) ++ "\n"  // instructions
+  def l(args: Any*): String = sc.s(args:_*) ++ ":\n"          // labels
+  def m(args: Any*): String = sc.s(args:_*) ++ "\n"           // methods
+}
+
+// variable / index environments
+type Env = Map[String, Int]
+
+// compile expressions
+def compile_exp(a: Exp, env : Env) : String = a match {
+  case Num(i) => i"ldc $i"
+  case Var(s) => i"iload ${env(s)}"
+  case Aop("+", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"iadd"
+  case Aop("-", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"isub"
+  case Aop("*", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"imul"
+  case Aop("/", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"idiv"
+  case Aop("%", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"irem"
+  case If(b, a1, a2) => {
+    val if_else = Fresh("If_else")
+    val if_end = Fresh("If_end")
+    compile_bexp(b, env, if_else) ++
+    compile_exp(a1, env) ++
+    i"goto $if_end" ++
+    l"$if_else" ++
+    compile_exp(a2, env) ++
+    l"$if_end"
+  }
+  case Call(name, args) => {
+    val is = "I" * args.length
+    args.map(a => compile_exp(a, env)).mkString ++
+    i"invokestatic XXX/XXX/$name($is)I"
+  }
+  case Sequ(a1, a2) => {
+    compile_exp(a1, env) ++ i"pop" ++ compile_exp(a2, env)
+  }
+  case Write(a1) => {
+    compile_exp(a1, env) ++
+    i"dup" ++
+    i"invokestatic XXX/XXX/write(I)V"
+  }
+}
+
+// compile boolean expressions
+def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match {
+  case Bop("==", a1, a2) => 
+    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpne $jmp"
+  case Bop("!=", a1, a2) => 
+    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpeq $jmp"
+  case Bop("<", a1, a2) => 
+    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpge $jmp"
+  case Bop("<=", a1, a2) => 
+    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpgt $jmp"
+}
+
+// compile functions and declarations
+def compile_decl(d: Decl) : String = d match {
+  case Def(name, args, a) => { 
+    val env = args.zipWithIndex.toMap
+    val is = "I" * args.length
+    m".method public static $name($is)I" ++
+    m".limit locals ${args.length.toString}" ++
+    m".limit stack ${1 + max_stack_exp(a)}" ++
+    l"${name}_Start" ++   
+    compile_exp(a, env) ++
+    i"ireturn" ++
+    m".end method\n"
+  }
+  case Main(a) => {
+    m".method public static main([Ljava/lang/String;)V" ++
+    m".limit locals 200" ++
+    m".limit stack 200" ++
+    compile_exp(a, Map()) ++
+    i"invokestatic XXX/XXX/write(I)V" ++
+    i"return" ++
+    m".end method\n"
+  }
+}
+
+// the main compilation function
+def compile(prog: List[Decl], class_name: String) : String = {
+  val instructions = prog.map(compile_decl).mkString
+  (library + instructions).replaceAllLiterally("XXX", class_name)
+}
+
+
+
+
+// An example program (two versions of factorial)
+//
+// def fact(n) = 
+//    if n == 0 then 1 else n * fact(n - 1);
+//
+// def facT(n, acc) = 
+//    if n == 0 then acc else facT(n - 1, n * acc);
+// 
+// fact(10) ; facT(10, 1)
+// 
+
+
+val test_prog = 
+  List(Def("fact", List("n"),
+         If(Bop("==",Var("n"),Num(0)),
+            Num(1),
+            Aop("*",Var("n"),
+                    Call("fact",List(Aop("-",Var("n"),Num(1))))))),
+
+       Def("facT",List("n", "acc"),
+         If(Bop("==",Var("n"),Num(0)),
+            Var("acc"),
+            Call("facT",List(Aop("-",Var("n"),Num(1)), 
+                             Aop("*",Var("n"),Var("acc")))))),
+
+       Main(Sequ(Write(Call("fact",List(Num(10)))),
+                 Write(Call("facT",List(Num(10), Num(1)))))))
+
+// prints out the JVM instructions
+@main
+def test() = 
+  println(compile(test_prog, "fact"))
--- a/progs/fun/fun.scala	Sat Jul 04 22:12:18 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,213 +0,0 @@
-// A Small Compiler for a Simple Functional Language
-// (includes an external lexer and parser)
-//
-// call with 
-//
-//     scala fun.scala fact
-//
-//     scala fun.scala defs
-//
-// this will generate a .j file and run the jasmin
-// assembler (installed at jvm/jasmin-2.4/jasmin.jar)
-// it runs the resulting JVM file twice for timing 
-// purposes.
-
-
-
-
-object Compiler {
-
-import java.io._  
-import scala.util._
-import scala.sys.process._
-
-// Abstract syntax trees for the Fun language
-abstract class Exp extends Serializable 
-abstract class BExp extends Serializable 
-abstract class Decl extends Serializable 
-
-case class Def(name: String, args: List[String], body: Exp) extends Decl
-case class Main(e: Exp) extends Decl
-
-case class Call(name: String, args: List[Exp]) extends Exp
-case class If(a: BExp, e1: Exp, e2: Exp) extends Exp
-case class Write(e: Exp) extends Exp
-case class Var(s: String) extends Exp
-case class Num(i: Int) extends Exp
-case class Aop(o: String, a1: Exp, a2: Exp) extends Exp
-case class Sequence(e1: Exp, e2: Exp) extends Exp
-case class Bop(o: String, a1: Exp, a2: Exp) extends BExp
-
-
-// compiler - built-in functions 
-// copied from http://www.ceng.metu.edu.tr/courses/ceng444/link/jvm-cpm.html
-//
-
-val library = """
-.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
-        invokevirtual java/io/PrintStream/println(I)V 
-        return 
-.end method
-
-"""
-
-// calculating the maximal needed stack size
-def max_stack_exp(e: Exp): Int = e match {
-  case Call(_, args) => args.map(max_stack_exp).sum
-  case If(a, e1, e2) => max_stack_bexp(a) + (List(max_stack_exp(e1), max_stack_exp(e2)).max)
-  case Write(e) => max_stack_exp(e) + 1
-  case Var(_) => 1
-  case Num(_) => 1
-  case Aop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
-  case Sequence(e1, e2) => List(max_stack_exp(e1), max_stack_exp(e2)).max
-}
-
-def max_stack_bexp(e: BExp): Int = e match {
-  case Bop(_, a1, a2) => max_stack_exp(a1) + max_stack_exp(a2)
-}
-
-
-// for generating new labels
-var counter = -1
-
-def Fresh(x: String) = {
-  counter += 1
-  x ++ "_" ++ counter.toString()
-}
-
-// convenient string interpolations 
-// for instructions, labels and methods
-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 m(args: Any*): String = sc.s(args:_*) ++ "\n"
-}
-
-
-type Env = Map[String, Int]
-
-// compile expressions
-def compile_exp(a: Exp, env : Env) : String = a match {
-  case Num(i) => i"ldc $i"
-  case Var(s) => i"iload ${env(s)}"
-  case Aop("+", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"iadd"
-  case Aop("-", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"isub"
-  case Aop("*", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"imul"
-  case Aop("/", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"idiv"
-  case Aop("%", a1, a2) => compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"irem"
-  case If(b, a1, a2) => {
-    val if_else = Fresh("If_else")
-    val if_end = Fresh("If_end")
-    compile_bexp(b, env, if_else) ++
-    compile_exp(a1, env) ++
-    i"goto $if_end" ++
-    l"$if_else" ++
-    compile_exp(a2, env) ++
-    l"$if_end"
-  }
-  case Call(name, args) => {
-    val is = "I" * args.length
-    args.map(a => compile_exp(a, env)).mkString ++
-    i"invokestatic XXX/XXX/$name($is)I"
-  }
-  case Sequence(a1, a2) => {
-    compile_exp(a1, env) ++ i"pop" ++ compile_exp(a2, env)
-  }
-  case Write(a1) => {
-    compile_exp(a1, env) ++
-    i"dup" ++
-    i"invokestatic XXX/XXX/write(I)V"
-  }
-}
-
-// compile boolean expressions
-def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match {
-  case Bop("==", a1, a2) => 
-    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpne $jmp"
-  case Bop("!=", a1, a2) => 
-    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpeq $jmp"
-  case Bop("<", a1, a2) => 
-    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpge $jmp"
-  case Bop("<=", a1, a2) => 
-    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpgt $jmp"
-}
-
-// compile function for declarations and main
-def compile_decl(d: Decl) : String = d match {
-  case Def(name, args, a) => { 
-    val env = args.zipWithIndex.toMap
-    val is = "I" * args.length
-    m".method public static $name($is)I" ++
-    m".limit locals ${args.length}" ++
-    m".limit stack ${1 + max_stack_exp(a)}" ++
-    l"${name}_Start" ++   
-    compile_exp(a, env) ++
-    i"ireturn" ++
-    m".end method\n"
-  }
-  case Main(a) => {
-    m".method public static main([Ljava/lang/String;)V" ++
-    m".limit locals 200" ++
-    m".limit stack 200" ++
-    compile_exp(a, Map()) ++
-    i"invokestatic XXX/XXX/write(I)V" ++
-    i"return" ++
-    m".end method\n"
-  }
-}
-
-// main compiler functions
-
-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 deserialise[T](fname: String) : Try[T] = {
-  import scala.util.Using
-  Using(new ObjectInputStream(new FileInputStream(fname))) {
-    in => in.readObject.asInstanceOf[T]
-  }
-}
-
-def compile(class_name: String) : String = {
-  val ast = deserialise[List[Decl]](class_name ++ ".prs").getOrElse(Nil) 
-  val instructions = ast.map(compile_decl).mkString
-  (library + instructions).replaceAllLiterally("XXX", class_name)
-}
-
-def compile_to_file(class_name: String) = {
-  val output = compile(class_name)
-  scala.tools.nsc.io.File(s"${class_name}.j").writeAll(output)
-}
-
-def compile_and_run(class_name: String) : Unit = {
-  compile_to_file(class_name)
-  (s"java -jar jvm/jasmin-2.4/jasmin.jar ${class_name}.j").!!
-  println("Time: " + time_needed(1, (s"java ${class_name}/${class_name}").!))
-}
-
-
-// some examples of .fun files
-//compile_to_file("fact")
-//compile_and_run("fact")
-//compile_and_run("defs")
-
-
-def main(args: Array[String]) : Unit = 
-   compile_and_run(args(0))
-
-
-}