added example file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/doc-src/IsarAdvanced/Codegen/Thy/examples/tree.ML	Wed Mar 21 08:07:19 2007 +0100
@@ -0,0 +1,74 @@
+structure ROOT = 
+struct
+
+structure Orderings = 
+struct
+
+type 'a ord = {less_eq : 'a -> 'a -> bool, less : 'a -> 'a -> bool};
+fun less_eq (A_:'a ord) = #less_eq A_;
+fun less (A_:'a ord) = #less A_;
+
+end; (*struct Orderings*)
+
+structure Code_Generator = 
+struct
+
+type 'a eq = {op_eq : 'a -> 'a -> bool};
+fun op_eq (A_:'a eq) = #op_eq A_;
+
+end; (*struct Code_Generator*)
+
+structure Nat = 
+struct
+
+datatype nat = Zero_nat | Suc of nat;
+
+fun op_eq_nat Zero_nat (Suc m) = false
+  | op_eq_nat (Suc n) Zero_nat = false
+  | op_eq_nat (Suc n) (Suc m) = op_eq_nat n m
+  | op_eq_nat Zero_nat Zero_nat = true;
+
+val eq_nat = {op_eq = op_eq_nat} : nat Code_Generator.eq;
+
+fun less_nat n (Suc m) = less_eq_nat n m
+  | less_nat n Zero_nat = false
+and less_eq_nat (Suc n) m = less_nat n m
+  | less_eq_nat Zero_nat m = true;
+
+val ord_nat = {less_eq = less_eq_nat, less = less_nat} :
+  nat Orderings.ord;
+
+end; (*struct Nat*)
+
+structure List = 
+struct
+
+datatype nibble = Nibble0 | Nibble1 | Nibble2 | Nibble3 | Nibble4 |
+  Nibble5 | Nibble6 | Nibble7 | Nibble8 | Nibble9 | NibbleA | NibbleB |
+  NibbleC | NibbleD | NibbleE | NibbleF;
+
+end; (*struct List*)
+
+structure Codegen = 
+struct
+
+datatype ('a, 'b) searchtree = Leaf of 'a * 'b |
+  Branch of ('a, 'b) searchtree * 'a * ('a, 'b) searchtree;
+
+fun update (A1_, A2_) (it, entry) (Branch (t1, key, t2)) =
+  (if Orderings.less_eq A2_ it key
+    then Branch (update (A1_, A2_) (it, entry) t1, key, t2)
+    else Branch (t1, key, update (A1_, A2_) (it, entry) t2))
+  | update (A1_, A2_) (it, entry) (Leaf (key, vala)) =
+    (if Code_Generator.op_eq A1_ it key then Leaf (key, entry)
+      else (if Orderings.less_eq A2_ it key
+             then Branch (Leaf (it, entry), it, Leaf (key, vala))
+             else Branch (Leaf (key, vala), it, Leaf (it, entry))));
+
+fun example n =
+  update (Nat.eq_nat, Nat.ord_nat) (n, [#"b", #"a", #"r"])
+    (Leaf (Nat.Zero_nat, [#"f", #"o", #"o"]));
+
+end; (*struct Codegen*)
+
+end; (*struct ROOT*)