proper Pattern.match and corresponding Envir.subst_term, instead of Envir.norm_term of unify-family;
theory Tree2
imports Main
begin
datatype ('a,'b) tree =
Leaf ("\<langle>\<rangle>") |
Node 'b "('a,'b)tree" 'a "('a,'b) tree" ("\<langle>_, _, _, _\<rangle>")
fun inorder :: "('a,'b)tree \<Rightarrow> 'a list" where
"inorder Leaf = []" |
"inorder (Node _ l a r) = inorder l @ a # inorder r"
fun height :: "('a,'b) tree \<Rightarrow> nat" where
"height Leaf = 0" |
"height (Node _ l a r) = max (height l) (height r) + 1"
end