diff -r 61a936be50c4 -r f345e89895f5 progs/lexer/toks.scala.orig
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/lexer/toks.scala.orig	Mon Jun 29 21:05:34 2020 +0100
@@ -0,0 +1,138 @@
+abstract class Token
+case object T_SEMI extends Token
+case object T_LPAREN extends Token
+case object T_RPAREN extends Token
+case class T_ID(s: String) extends Token
+case class T_OP(s: String) extends Token
+case class T_NUM(n: Int) extends Token
+case class T_KWD(s: String) extends Token
+case class T_STR(s: String) extends Token
+
+
+// Loops program
+//===============
+
+/*
+start := 1000; 
+x := start;
+y := start;
+z := start;
+while 0 < x do {
+ while 0 < y do {
+  while 0 < z do { z := z - 1 };
+  z := start;
+  y := y - 1
+ };     
+ y := start;
+ x := x - 1
+}
+*/
+
+val loops =
+  List(T_ID("start"), T_OP(":="), T_NUM(1000), T_SEMI, T_ID("x"), T_OP(":="), 
+       T_ID("start"), T_SEMI, T_ID("y"), T_OP(":="), T_ID("start"), T_SEMI, 
+       T_ID("z"), T_OP(":="), T_ID("start"), T_SEMI, T_KWD("while"), T_NUM(0), 
+       T_OP("<"), T_ID("x"), T_KWD("do"), T_LPAREN, T_KWD("while"), T_NUM(0), 
+       T_OP("<"), T_ID("y"), T_KWD("do"), T_LPAREN, T_KWD("while"), T_NUM(0), 
+       T_OP("<"), T_ID("z"), T_KWD("do"), T_LPAREN, T_ID("z"), T_OP(":="), 
+       T_ID("z"), T_OP("-"), T_NUM(1), T_RPAREN, T_SEMI, T_ID("z"), T_OP(":="),
+       T_ID("start"), T_SEMI, T_ID("y"), T_OP(":="), T_ID("y"), T_OP("-"), 
+       T_NUM(1), T_RPAREN, T_SEMI, T_ID("y"), T_OP(":="), T_ID("start"), 
+       T_SEMI, T_ID("x"), T_OP(":="), T_ID("x"), T_OP("-"), T_NUM(1), T_RPAREN) 
+
+
+
+
+// Fib program
+//=============
+
+/*
+write "Fib";
+read n;  
+minus1 := 0;
+minus2 := 1;
+while n > 0 do {
+       temp := minus2;
+       minus2 := minus1 + minus2;
+       minus1 := temp;
+       n := n - 1
+};
+write "Result";
+write minus2
+*/
+
+val fib =
+  List(T_KWD("write"), T_STR("Fib"), T_SEMI, T_KWD("read"), T_ID("n"), 
+       T_SEMI, T_ID("minus1"), T_OP(":="), T_NUM(0), T_SEMI, T_ID("minus2"), 
+       T_OP(":="), T_NUM(1), T_SEMI, T_KWD("while"), T_ID("n"), T_OP(">"), 
+       T_NUM(0), T_KWD("do"), T_LPAREN, T_ID("temp"), T_OP(":="), 
+       T_ID("minus2"), T_SEMI, T_ID("minus2"), T_OP(":="), T_ID("minus1"), 
+       T_OP("+"), T_ID("minus2"), T_SEMI, T_ID("minus1"), T_OP(":="), 
+       T_ID("temp"), T_SEMI, T_ID("n"), T_OP(":="), T_ID("n"), T_OP("-"), 
+       T_NUM(1), T_RPAREN, T_SEMI, T_KWD("write"), T_STR("Result"), T_SEMI, 
+       T_KWD("write"), T_ID("minus2"))
+
+
+
+// Factors program
+//=================
+
+/*
+write "Input n please";
+read n;
+write "The factors of n are";
+f := 2;
+while n != 1 do {
+    while (n / f) * f == n do {
+        write f;
+        n := n / f
+    };
+    f := f + 1
+}
+*/
+
+val factors = 
+  List(T_KWD("write"), T_STR("Input n please"), T_SEMI, T_KWD("read"), 
+       T_ID("n"), T_SEMI, T_KWD("write"), T_STR("The factors of n are"), 
+       T_SEMI, T_ID("f"), T_OP(":="), T_NUM(2), T_SEMI, T_KWD("while"), 
+       T_ID("n"), T_OP("!="), T_NUM(1), T_KWD("do"), T_LPAREN, 
+       T_KWD("while"), T_ID("n"), T_OP("/"), T_ID("f"), T_OP("*"), 
+       T_ID("f"), T_OP("=="), T_ID("n"), T_KWD("do"), T_LPAREN, 
+       T_KWD("write"), T_ID("f"), T_SEMI, T_ID("n"), T_OP(":="), 
+       T_ID("n"), T_OP("/"), T_ID("f"), T_RPAREN, T_SEMI, T_ID("f"), 
+       T_OP(":="), T_ID("f"), T_OP("+"), T_NUM(1), T_RPAREN)
+
+
+// Primes program
+//================
+
+/*
+end := 100;
+n := 2;
+while (n < end) do {
+  f := 2;
+  tmp := 0;
+  while ((f < n / 2 + 1) && (tmp == 0)) do {
+    if ((n / f) * f == n) then  { tmp := 1 } else { skip };
+    f := f + 1
+  };
+  if (tmp == 0) then { write(n) } else { skip };
+  n  := n + 1
+}
+*/
+
+val primes =
+  List(T_ID("end"), T_OP(":="), T_NUM(100), T_SEMI, T_ID("n"), T_OP(":="), 
+       T_NUM(2), T_SEMI, T_KWD("while"), T_ID("n"), T_OP("<"), T_ID("end"), 
+       T_KWD("do"), T_LPAREN, T_ID("f"), T_OP(":="), T_NUM(2), T_SEMI, 
+       T_ID("tmp"), T_OP(":="), T_NUM(0), T_SEMI, T_KWD("while"), T_ID("f"), 
+       T_OP("<"), T_ID("n"), T_OP("/"), T_NUM(2), T_OP("+"), T_NUM(1), 
+       T_OP("&&"), T_ID("tmp"), T_OP("=="), T_NUM(0), T_KWD("do"), T_LPAREN, 
+       T_KWD("if"), T_ID("n"), T_OP("/"), T_ID("f"), T_OP("*"), T_ID("f"), 
+       T_OP("=="), T_ID("n"), T_KWD("then"), T_LPAREN, T_ID("tmp"), T_OP(":="),
+       T_NUM(1), T_RPAREN, T_KWD("else"), T_LPAREN, T_KWD("skip"), T_RPAREN, 
+       T_SEMI, T_ID("f"), T_OP(":="), T_ID("f"), T_OP("+"), T_NUM(1), 
+       T_RPAREN, T_SEMI, T_KWD("if"), T_ID("tmp"), T_OP("=="), T_NUM(0), 
+       T_KWD("then"), T_LPAREN, T_KWD("write"), T_ID("n"), T_RPAREN, 
+       T_KWD("else"), T_LPAREN, T_KWD("skip"), T_RPAREN, T_SEMI, T_ID("n"), 
+       T_OP(":="), T_ID("n"), T_OP("+"), T_NUM(1), T_RPAREN)