header {* Powerdomain examples *}
theory Powerdomain_ex
imports HOLCF
begin
default_sort bifinite
subsection {* Monadic sorting example *}
domain ordering = LT | EQ | GT
definition
compare :: "int lift -> int lift -> ordering" where
"compare = (FLIFT x y. if x < y then LT else if x = y then EQ else GT)"
definition
is_le :: "int lift -> int lift -> tr" where
"is_le = (Λ x y. case compare·x·y of LT => TT | EQ => TT | GT => FF)"
definition
is_less :: "int lift -> int lift -> tr" where
"is_less = (Λ x y. case compare·x·y of LT => TT | EQ => FF | GT => FF)"
definition
r1 :: "(int lift × 'a) -> (int lift × 'a) -> tr convex_pd" where
"r1 = (Λ (x,_) (y,_). case compare·x·y of
LT => {TT}\<natural> |
EQ => {TT, FF}\<natural> |
GT => {FF}\<natural>)"
definition
r2 :: "(int lift × 'a) -> (int lift × 'a) -> tr convex_pd" where
"r2 = (Λ (x,_) (y,_). {is_le·x·y, is_less·x·y}\<natural>)"
lemma r1_r2: "r1·(x,a)·(y,b) = (r2·(x,a)·(y,b) :: tr convex_pd)"
apply (simp add: r1_def r2_def)
apply (simp add: is_le_def is_less_def)
apply (cases "compare·x·y")
apply simp_all
done
subsection {* Picking a leaf from a tree *}
domain 'a tree =
Node (lazy "'a tree") (lazy "'a tree") |
Leaf (lazy "'a")
fixrec
mirror :: "'a tree -> 'a tree"
where
mirror_Leaf: "mirror·(Leaf·a) = Leaf·a"
| mirror_Node: "mirror·(Node·l·r) = Node·(mirror·r)·(mirror·l)"
lemma mirror_strict [simp]: "mirror·⊥ = ⊥"
by fixrec_simp
fixrec
pick :: "'a tree -> 'a convex_pd"
where
pick_Leaf: "pick·(Leaf·a) = {a}\<natural>"
| pick_Node: "pick·(Node·l·r) = pick·l +\<natural> pick·r"
lemma pick_strict [simp]: "pick·⊥ = ⊥"
by fixrec_simp
lemma pick_mirror: "pick·(mirror·t) = pick·t"
by (induct t) (simp_all add: convex_plus_ac)
fixrec tree1 :: "int lift tree"
where "tree1 = Node·(Node·(Leaf·(Def 1))·(Leaf·(Def 2)))
·(Node·(Leaf·(Def 3))·(Leaf·(Def 4)))"
fixrec tree2 :: "int lift tree"
where "tree2 = Node·(Node·(Leaf·(Def 1))·(Leaf·(Def 2)))
·(Node·⊥·(Leaf·(Def 4)))"
fixrec tree3 :: "int lift tree"
where "tree3 = Node·(Node·(Leaf·(Def 1))·tree3)
·(Node·(Leaf·(Def 3))·(Leaf·(Def 4)))"
declare tree1.simps tree2.simps tree3.simps [simp del]
lemma pick_tree1:
"pick·tree1 = {Def 1, Def 2, Def 3, Def 4}\<natural>"
apply (subst tree1.simps)
apply simp
apply (simp add: convex_plus_ac)
done
lemma pick_tree2:
"pick·tree2 = {Def 1, Def 2, ⊥, Def 4}\<natural>"
apply (subst tree2.simps)
apply simp
apply (simp add: convex_plus_ac)
done
lemma pick_tree3:
"pick·tree3 = {Def 1, ⊥, Def 3, Def 4}\<natural>"
apply (subst tree3.simps)
apply simp
apply (induct rule: tree3.induct)
apply simp
apply simp
apply (simp add: convex_plus_ac)
apply simp
apply (simp add: convex_plus_ac)
done
end