Theory HOL-Library.Extended_Nat
section ‹Extended natural numbers (i.e. with infinity)›
theory Extended_Nat
imports Main Countable Order_Continuity
begin
class infinity =
fixes infinity :: "'a" ("∞")
context
fixes f :: "nat ⇒ 'a::{canonically_ordered_monoid_add, linorder_topology, complete_linorder}"
begin
lemma sums_SUP[simp, intro]: "f sums (SUP n. ∑i<n. f i)"
unfolding sums_def by (intro LIMSEQ_SUP monoI sum_mono2 zero_le) auto
lemma suminf_eq_SUP: "suminf f = (SUP n. ∑i<n. f i)"
using sums_SUP by (rule sums_unique[symmetric])
end
subsection ‹Type definition›
text ‹
We extend the standard natural numbers by a special value indicating
infinity.
›
typedef enat = "UNIV :: nat option set" ..
text ‹TODO: introduce enat as coinductive datatype, enat is just \<^const>‹of_nat››
definition enat :: "nat ⇒ enat" where
"enat n = Abs_enat (Some n)"
instantiation enat :: infinity
begin
definition "∞ = Abs_enat None"
instance ..
end
instance enat :: countable
proof
show "∃to_nat::enat ⇒ nat. inj to_nat"
by (rule exI[of _ "to_nat ∘ Rep_enat"]) (simp add: inj_on_def Rep_enat_inject)
qed
old_rep_datatype enat "∞ :: enat"
proof -
fix P i assume "⋀j. P (enat j)" "P ∞"
then show "P i"
proof induct
case (Abs_enat y) then show ?case
by (cases y rule: option.exhaust)
(auto simp: enat_def infinity_enat_def)
qed
qed (auto simp add: enat_def infinity_enat_def Abs_enat_inject)
declare [[coercion "enat::nat⇒enat"]]
lemmas enat2_cases = enat.exhaust[case_product enat.exhaust]
lemmas enat3_cases = enat.exhaust[case_product enat.exhaust enat.exhaust]
lemma not_infinity_eq [iff]: "(x ≠ ∞) = (∃i. x = enat i)"
by (cases x) auto
lemma not_enat_eq [iff]: "(∀y. x ≠ enat y) = (x = ∞)"
by (cases x) auto
lemma enat_ex_split: "(∃c::enat. P c) ⟷ P ∞ ∨ (∃c::nat. P c)"
by (metis enat.exhaust)
primrec the_enat :: "enat ⇒ nat"
where "the_enat (enat n) = n"
subsection ‹Constructors and numbers›
instantiation enat :: zero_neq_one
begin
definition
"0 = enat 0"
definition
"1 = enat 1"
instance
proof qed (simp add: zero_enat_def one_enat_def)
end
definition eSuc :: "enat ⇒ enat" where
"eSuc i = (case i of enat n ⇒ enat (Suc n) | ∞ ⇒ ∞)"
lemma enat_0 [code_post]: "enat 0 = 0"
by (simp add: zero_enat_def)
lemma enat_1 [code_post]: "enat 1 = 1"
by (simp add: one_enat_def)
lemma enat_0_iff: "enat x = 0 ⟷ x = 0" "0 = enat x ⟷ x = 0"
by (auto simp add: zero_enat_def)
lemma enat_1_iff: "enat x = 1 ⟷ x = 1" "1 = enat x ⟷ x = 1"
by (auto simp add: one_enat_def)
lemma one_eSuc: "1 = eSuc 0"
by (simp add: zero_enat_def one_enat_def eSuc_def)
lemma infinity_ne_i0 [simp]: "(∞::enat) ≠ 0"
by (simp add: zero_enat_def)
lemma i0_ne_infinity [simp]: "0 ≠ (∞::enat)"
by (simp add: zero_enat_def)
lemma zero_one_enat_neq:
"¬ 0 = (1::enat)"
"¬ 1 = (0::enat)"
unfolding zero_enat_def one_enat_def by simp_all
lemma infinity_ne_i1 [simp]: "(∞::enat) ≠ 1"
by (simp add: one_enat_def)
lemma i1_ne_infinity [simp]: "1 ≠ (∞::enat)"
by (simp add: one_enat_def)
lemma eSuc_enat: "eSuc (enat n) = enat (Suc n)"
by (simp add: eSuc_def)
lemma eSuc_infinity [simp]: "eSuc ∞ = ∞"
by (simp add: eSuc_def)
lemma eSuc_ne_0 [simp]: "eSuc n ≠ 0"
by (simp add: eSuc_def zero_enat_def split: enat.splits)
lemma zero_ne_eSuc [simp]: "0 ≠ eSuc n"
by (rule eSuc_ne_0 [symmetric])
lemma eSuc_inject [simp]: "eSuc m = eSuc n ⟷ m = n"
by (simp add: eSuc_def split: enat.splits)
lemma eSuc_enat_iff: "eSuc x = enat y ⟷ (∃n. y = Suc n ∧ x = enat n)"
by (cases y) (auto simp: enat_0 eSuc_enat[symmetric])
lemma enat_eSuc_iff: "enat y = eSuc x ⟷ (∃n. y = Suc n ∧ enat n = x)"
by (cases y) (auto simp: enat_0 eSuc_enat[symmetric])
subsection ‹Addition›
instantiation enat :: comm_monoid_add
begin
definition [nitpick_simp]:
"m + n = (case m of ∞ ⇒ ∞ | enat m ⇒ (case n of ∞ ⇒ ∞ | enat n ⇒ enat (m + n)))"
lemma plus_enat_simps [simp, code]:
fixes q :: enat
shows "enat m + enat n = enat (m + n)"
and "∞ + q = ∞"
and "q + ∞ = ∞"
by (simp_all add: plus_enat_def split: enat.splits)
instance
proof
fix n m q :: enat
show "n + m + q = n + (m + q)"
by (cases n m q rule: enat3_cases) auto
show "n + m = m + n"
by (cases n m rule: enat2_cases) auto
show "0 + n = n"
by (cases n) (simp_all add: zero_enat_def)
qed
end
lemma eSuc_plus_1:
"eSuc n = n + 1"
by (cases n) (simp_all add: eSuc_enat one_enat_def)
lemma plus_1_eSuc:
"1 + q = eSuc q"
"q + 1 = eSuc q"
by (simp_all add: eSuc_plus_1 ac_simps)
lemma iadd_Suc: "eSuc m + n = eSuc (m + n)"
by (simp_all add: eSuc_plus_1 ac_simps)
lemma iadd_Suc_right: "m + eSuc n = eSuc (m + n)"
by (simp only: add.commute[of m] iadd_Suc)
subsection ‹Multiplication›
instantiation enat :: "{comm_semiring_1, semiring_no_zero_divisors}"
begin
definition times_enat_def [nitpick_simp]:
"m * n = (case m of ∞ ⇒ if n = 0 then 0 else ∞ | enat m ⇒
(case n of ∞ ⇒ if m = 0 then 0 else ∞ | enat n ⇒ enat (m * n)))"
lemma times_enat_simps [simp, code]:
"enat m * enat n = enat (m * n)"
"∞ * ∞ = (∞::enat)"
"∞ * enat n = (if n = 0 then 0 else ∞)"
"enat m * ∞ = (if m = 0 then 0 else ∞)"
unfolding times_enat_def zero_enat_def
by (simp_all split: enat.split)
instance
proof
fix a b c :: enat
show "(a * b) * c = a * (b * c)"
unfolding times_enat_def zero_enat_def
by (simp split: enat.split)
show comm: "a * b = b * a"
unfolding times_enat_def zero_enat_def
by (simp split: enat.split)
show "1 * a = a"
unfolding times_enat_def zero_enat_def one_enat_def
by (simp split: enat.split)
show distr: "(a + b) * c = a * c + b * c"
unfolding times_enat_def zero_enat_def
by (simp split: enat.split add: distrib_right)
show "0 * a = 0"
unfolding times_enat_def zero_enat_def
by (simp split: enat.split)
show "a * 0 = 0"
unfolding times_enat_def zero_enat_def
by (simp split: enat.split)
show "a * (b + c) = a * b + a * c"
by (cases a b c rule: enat3_cases) (auto simp: times_enat_def zero_enat_def distrib_left)
show "a ≠ 0 ⟹ b ≠ 0 ⟹ a * b ≠ 0"
by (cases a b rule: enat2_cases) (auto simp: times_enat_def zero_enat_def)
qed
end
lemma mult_eSuc: "eSuc m * n = n + m * n"
unfolding eSuc_plus_1 by (simp add: algebra_simps)
lemma mult_eSuc_right: "m * eSuc n = m + m * n"
unfolding eSuc_plus_1 by (simp add: algebra_simps)
lemma of_nat_eq_enat: "of_nat n = enat n"
apply (induct n)
apply (simp add: enat_0)
apply (simp add: plus_1_eSuc eSuc_enat)
done
instance enat :: semiring_char_0
proof
have "inj enat" by (rule injI) simp
then show "inj (λn. of_nat n :: enat)" by (simp add: of_nat_eq_enat)
qed
lemma imult_is_infinity: "((a::enat) * b = ∞) = (a = ∞ ∧ b ≠ 0 ∨ b = ∞ ∧ a ≠ 0)"
by (auto simp add: times_enat_def zero_enat_def split: enat.split)
subsection ‹Numerals›
lemma numeral_eq_enat:
"numeral k = enat (numeral k)"
using of_nat_eq_enat [of "numeral k"] by simp
lemma enat_numeral [code_abbrev]:
"enat (numeral k) = numeral k"
using numeral_eq_enat ..
lemma infinity_ne_numeral [simp]: "(∞::enat) ≠ numeral k"
by (simp add: numeral_eq_enat)
lemma numeral_ne_infinity [simp]: "numeral k ≠ (∞::enat)"
by (simp add: numeral_eq_enat)
lemma eSuc_numeral [simp]: "eSuc (numeral k) = numeral (k + Num.One)"
by (simp only: eSuc_plus_1 numeral_plus_one)
subsection ‹Subtraction›
instantiation enat :: minus
begin
definition diff_enat_def:
"a - b = (case a of (enat x) ⇒ (case b of (enat y) ⇒ enat (x - y) | ∞ ⇒ 0)
| ∞ ⇒ ∞)"
instance ..
end
lemma idiff_enat_enat [simp, code]: "enat a - enat b = enat (a - b)"
by (simp add: diff_enat_def)
lemma idiff_infinity [simp, code]: "∞ - n = (∞::enat)"
by (simp add: diff_enat_def)
lemma idiff_infinity_right [simp, code]: "enat a - ∞ = 0"
by (simp add: diff_enat_def)
lemma idiff_0 [simp]: "(0::enat) - n = 0"
by (cases n, simp_all add: zero_enat_def)
lemmas idiff_enat_0 [simp] = idiff_0 [unfolded zero_enat_def]
lemma idiff_0_right [simp]: "(n::enat) - 0 = n"
by (cases n) (simp_all add: zero_enat_def)
lemmas idiff_enat_0_right [simp] = idiff_0_right [unfolded zero_enat_def]
lemma idiff_self [simp]: "n ≠ ∞ ⟹ (n::enat) - n = 0"
by (auto simp: zero_enat_def)
lemma eSuc_minus_eSuc [simp]: "eSuc n - eSuc m = n - m"
by (simp add: eSuc_def split: enat.split)
lemma eSuc_minus_1 [simp]: "eSuc n - 1 = n"
by (simp add: one_enat_def flip: eSuc_enat zero_enat_def)
subsection ‹Ordering›
instantiation enat :: linordered_ab_semigroup_add
begin
definition [nitpick_simp]:
"m ≤ n = (case n of enat n1 ⇒ (case m of enat m1 ⇒ m1 ≤ n1 | ∞ ⇒ False)
| ∞ ⇒ True)"
definition [nitpick_simp]:
"m < n = (case m of enat m1 ⇒ (case n of enat n1 ⇒ m1 < n1 | ∞ ⇒ True)
| ∞ ⇒ False)"
lemma enat_ord_simps [simp]:
"enat m ≤ enat n ⟷ m ≤ n"
"enat m < enat n ⟷ m < n"
"q ≤ (∞::enat)"
"q < (∞::enat) ⟷ q ≠ ∞"
"(∞::enat) ≤ q ⟷ q = ∞"
"(∞::enat) < q ⟷ False"
by (simp_all add: less_eq_enat_def less_enat_def split: enat.splits)
lemma numeral_le_enat_iff[simp]:
shows "numeral m ≤ enat n ⟷ numeral m ≤ n"
by (auto simp: numeral_eq_enat)
lemma numeral_less_enat_iff[simp]:
shows "numeral m < enat n ⟷ numeral m < n"
by (auto simp: numeral_eq_enat)
lemma enat_ord_code [code]:
"enat m ≤ enat n ⟷ m ≤ n"
"enat m < enat n ⟷ m < n"
"q ≤ (∞::enat) ⟷ True"
"enat m < ∞ ⟷ True"
"∞ ≤ enat n ⟷ False"
"(∞::enat) < q ⟷ False"
by simp_all
instance
by standard (auto simp add: less_eq_enat_def less_enat_def plus_enat_def split: enat.splits)
end
instance enat :: dioid
proof
fix a b :: enat show "(a ≤ b) = (∃c. b = a + c)"
by (cases a b rule: enat2_cases) (auto simp: le_iff_add enat_ex_split)
qed
instance enat :: "{linordered_nonzero_semiring, strict_ordered_comm_monoid_add}"
proof
fix a b c :: enat
show "a ≤ b ⟹ 0 ≤ c ⟹c * a ≤ c * b"
unfolding times_enat_def less_eq_enat_def zero_enat_def
by (simp split: enat.splits)
show "a < b ⟹ c < d ⟹ a + c < b + d" for a b c d :: enat
by (cases a b c d rule: enat2_cases[case_product enat2_cases]) auto
show "a < b ⟹ a + 1 < b + 1"
by (metis add_right_mono eSuc_minus_1 eSuc_plus_1 less_le)
qed (simp add: zero_enat_def one_enat_def)
lemma add_diff_assoc_enat: "z ≤ y ⟹ x + (y - z) = x + y - (z::enat)"
by(cases x)(auto simp add: diff_enat_def split: enat.split)
lemma enat_ord_number [simp]:
"(numeral m :: enat) ≤ numeral n ⟷ (numeral m :: nat) ≤ numeral n"
"(numeral m :: enat) < numeral n ⟷ (numeral m :: nat) < numeral n"
by (simp_all add: numeral_eq_enat)
lemma infinity_ileE [elim!]: "∞ ≤ enat m ⟹ R"
by (simp add: zero_enat_def less_eq_enat_def split: enat.splits)
lemma infinity_ilessE [elim!]: "∞ < enat m ⟹ R"
by simp
lemma eSuc_ile_mono [simp]: "eSuc n ≤ eSuc m ⟷ n ≤ m"
by (simp add: eSuc_def less_eq_enat_def split: enat.splits)
lemma eSuc_mono [simp]: "eSuc n < eSuc m ⟷ n < m"
by (simp add: eSuc_def less_enat_def split: enat.splits)
lemma ile_eSuc [simp]: "n ≤ eSuc n"
by (simp add: eSuc_def less_eq_enat_def split: enat.splits)
lemma not_eSuc_ilei0 [simp]: "¬ eSuc n ≤ 0"
by (simp add: zero_enat_def eSuc_def less_eq_enat_def split: enat.splits)
lemma i0_iless_eSuc [simp]: "0 < eSuc n"
by (simp add: zero_enat_def eSuc_def less_enat_def split: enat.splits)
lemma iless_eSuc0[simp]: "(n < eSuc 0) = (n = 0)"
by (simp add: zero_enat_def eSuc_def less_enat_def split: enat.split)
lemma ileI1: "m < n ⟹ eSuc m ≤ n"
by (simp add: eSuc_def less_eq_enat_def less_enat_def split: enat.splits)
lemma Suc_ile_eq: "enat (Suc m) ≤ n ⟷ enat m < n"
by (cases n) auto
lemma iless_Suc_eq [simp]: "enat m < eSuc n ⟷ enat m ≤ n"
by (auto simp add: eSuc_def less_enat_def split: enat.splits)
lemma imult_infinity: "(0::enat) < n ⟹ ∞ * n = ∞"
by (simp add: zero_enat_def less_enat_def split: enat.splits)
lemma imult_infinity_right: "(0::enat) < n ⟹ n * ∞ = ∞"
by (simp add: zero_enat_def less_enat_def split: enat.splits)
lemma enat_0_less_mult_iff: "(0 < (m::enat) * n) = (0 < m ∧ 0 < n)"
by (simp only: zero_less_iff_neq_zero mult_eq_0_iff, simp)
lemma mono_eSuc: "mono eSuc"
by (simp add: mono_def)
lemma min_enat_simps [simp]:
"min (enat m) (enat n) = enat (min m n)"
"min q 0 = 0"
"min 0 q = 0"
"min q (∞::enat) = q"
"min (∞::enat) q = q"
by (auto simp add: min_def)
lemma max_enat_simps [simp]:
"max (enat m) (enat n) = enat (max m n)"
"max q 0 = q"
"max 0 q = q"
"max q ∞ = (∞::enat)"
"max ∞ q = (∞::enat)"
by (simp_all add: max_def)
lemma enat_ile: "n ≤ enat m ⟹ ∃k. n = enat k"
by (cases n) simp_all
lemma enat_iless: "n < enat m ⟹ ∃k. n = enat k"
by (cases n) simp_all
lemma iadd_le_enat_iff:
"x + y ≤ enat n ⟷ (∃y' x'. x = enat x' ∧ y = enat y' ∧ x' + y' ≤ n)"
by(cases x y rule: enat.exhaust[case_product enat.exhaust]) simp_all
lemma chain_incr: "∀i. ∃j. Y i < Y j ⟹ ∃j. enat k < Y j"
apply (induct_tac k)
apply (simp (no_asm) only: enat_0)
apply (fast intro: le_less_trans [OF zero_le])
apply (erule exE)
apply (drule spec)
apply (erule exE)
apply (drule ileI1)
apply (rule eSuc_enat [THEN subst])
apply (rule exI)
apply (erule (1) le_less_trans)
done
lemma eSuc_max: "eSuc (max x y) = max (eSuc x) (eSuc y)"
by (simp add: eSuc_def split: enat.split)
lemma eSuc_Max:
assumes "finite A" "A ≠ {}"
shows "eSuc (Max A) = Max (eSuc ` A)"
using assms proof induction
case (insert x A)
thus ?case by(cases "A = {}")(simp_all add: eSuc_max)
qed simp
instantiation enat :: "{order_bot, order_top}"
begin
definition bot_enat :: enat where "bot_enat = 0"
definition top_enat :: enat where "top_enat = ∞"
instance
by standard (simp_all add: bot_enat_def top_enat_def)
end
lemma finite_enat_bounded:
assumes le_fin: "⋀y. y ∈ A ⟹ y ≤ enat n"
shows "finite A"
proof (rule finite_subset)
show "finite (enat ` {..n})" by blast
have "A ⊆ {..enat n}" using le_fin by fastforce
also have "… ⊆ enat ` {..n}"
apply (rule subsetI)
subgoal for x by (cases x) auto
done
finally show "A ⊆ enat ` {..n}" .
qed
subsection ‹Cancellation simprocs›
lemma add_diff_cancel_enat[simp]: "x ≠ ∞ ⟹ x + y - x = (y::enat)"
by (metis add.commute add.right_neutral add_diff_assoc_enat idiff_self order_refl)
lemma enat_add_left_cancel: "a + b = a + c ⟷ a = (∞::enat) ∨ b = c"
unfolding plus_enat_def by (simp split: enat.split)
lemma enat_add_left_cancel_le: "a + b ≤ a + c ⟷ a = (∞::enat) ∨ b ≤ c"
unfolding plus_enat_def by (simp split: enat.split)
lemma enat_add_left_cancel_less: "a + b < a + c ⟷ a ≠ (∞::enat) ∧ b < c"
unfolding plus_enat_def by (simp split: enat.split)
lemma plus_eq_infty_iff_enat: "(m::enat) + n = ∞ ⟷ m=∞ ∨ n=∞"
using enat_add_left_cancel by fastforce
ML ‹
structure Cancel_Enat_Common =
struct
fun find_first_t _ _ [] = raise TERM("find_first_t", [])
| find_first_t past u (t::terms) =
if u aconv t then (rev past @ terms)
else find_first_t (t::past) u terms
fun dest_summing (Const (\<^const_name>‹Groups.plus›, _) $ t $ u, ts) =
dest_summing (t, dest_summing (u, ts))
| dest_summing (t, ts) = t :: ts
val mk_sum = Arith_Data.long_mk_sum
fun dest_sum t = dest_summing (t, [])
val find_first = find_first_t []
val trans_tac = Numeral_Simprocs.trans_tac
val norm_ss =
simpset_of (put_simpset HOL_basic_ss \<^context>
addsimps @{thms ac_simps add_0_left add_0_right})
fun norm_tac ctxt = ALLGOALS (simp_tac (put_simpset norm_ss ctxt))
fun simplify_meta_eq ctxt cancel_th th =
Arith_Data.simplify_meta_eq [] ctxt
([th, cancel_th] MRS trans)
fun mk_eq (a, b) = HOLogic.mk_Trueprop (HOLogic.mk_eq (a, b))
end
structure Eq_Enat_Cancel = ExtractCommonTermFun
(open Cancel_Enat_Common
val mk_bal = HOLogic.mk_eq
val dest_bal = HOLogic.dest_bin \<^const_name>‹HOL.eq› \<^typ>‹enat›
fun simp_conv _ _ = SOME @{thm enat_add_left_cancel}
)
structure Le_Enat_Cancel = ExtractCommonTermFun
(open Cancel_Enat_Common
val mk_bal = HOLogic.mk_binrel \<^const_name>‹Orderings.less_eq›
val dest_bal = HOLogic.dest_bin \<^const_name>‹Orderings.less_eq› \<^typ>‹enat›
fun simp_conv _ _ = SOME @{thm enat_add_left_cancel_le}
)
structure Less_Enat_Cancel = ExtractCommonTermFun
(open Cancel_Enat_Common
val mk_bal = HOLogic.mk_binrel \<^const_name>‹Orderings.less›
val dest_bal = HOLogic.dest_bin \<^const_name>‹Orderings.less› \<^typ>‹enat›
fun simp_conv _ _ = SOME @{thm enat_add_left_cancel_less}
)
›
simproc_setup enat_eq_cancel
("(l::enat) + m = n" | "(l::enat) = m + n") =
‹fn phi => fn ctxt => fn ct => Eq_Enat_Cancel.proc ctxt (Thm.term_of ct)›
simproc_setup enat_le_cancel
("(l::enat) + m ≤ n" | "(l::enat) ≤ m + n") =
‹fn phi => fn ctxt => fn ct => Le_Enat_Cancel.proc ctxt (Thm.term_of ct)›
simproc_setup enat_less_cancel
("(l::enat) + m < n" | "(l::enat) < m + n") =
‹fn phi => fn ctxt => fn ct => Less_Enat_Cancel.proc ctxt (Thm.term_of ct)›
text ‹TODO: add regression tests for these simprocs›
text ‹TODO: add simprocs for combining and cancelling numerals›
subsection ‹Well-ordering›
lemma less_enatE:
"[| n < enat m; !!k. n = enat k ==> k < m ==> P |] ==> P"
by (induct n) auto
lemma less_infinityE:
"[| n < ∞; !!k. n = enat k ==> P |] ==> P"
by (induct n) auto
lemma enat_less_induct:
assumes prem: "⋀n. ∀m::enat. m < n ⟶ P m ⟹ P n" shows "P n"
proof -
have P_enat: "⋀k. P (enat k)"
apply (rule nat_less_induct)
apply (rule prem, clarify)
apply (erule less_enatE, simp)
done
show ?thesis
proof (induct n)
fix nat
show "P (enat nat)" by (rule P_enat)
next
show "P ∞"
apply (rule prem, clarify)
apply (erule less_infinityE)
apply (simp add: P_enat)
done
qed
qed
instance enat :: wellorder
proof
fix P and n
assume hyp: "(⋀n::enat. (⋀m::enat. m < n ⟹ P m) ⟹ P n)"
show "P n" by (blast intro: enat_less_induct hyp)
qed
subsection ‹Complete Lattice›
instantiation enat :: complete_lattice
begin
definition inf_enat :: "enat ⇒ enat ⇒ enat" where
"inf_enat = min"
definition sup_enat :: "enat ⇒ enat ⇒ enat" where
"sup_enat = max"
definition Inf_enat :: "enat set ⇒ enat" where
"Inf_enat A = (if A = {} then ∞ else (LEAST x. x ∈ A))"
definition Sup_enat :: "enat set ⇒ enat" where
"Sup_enat A = (if A = {} then 0 else if finite A then Max A else ∞)"
instance
proof
fix x :: "enat" and A :: "enat set"
{ assume "x ∈ A" then show "Inf A ≤ x"
unfolding Inf_enat_def by (auto intro: Least_le) }
{ assume "⋀y. y ∈ A ⟹ x ≤ y" then show "x ≤ Inf A"
unfolding Inf_enat_def
by (cases "A = {}") (auto intro: LeastI2_ex) }
{ assume "x ∈ A" then show "x ≤ Sup A"
unfolding Sup_enat_def by (cases "finite A") auto }
{ assume "⋀y. y ∈ A ⟹ y ≤ x" then show "Sup A ≤ x"
unfolding Sup_enat_def using finite_enat_bounded by auto }
qed (simp_all add:
inf_enat_def sup_enat_def bot_enat_def top_enat_def Inf_enat_def Sup_enat_def)
end
instance enat :: complete_linorder ..
lemma eSuc_Sup: "A ≠ {} ⟹ eSuc (Sup A) = Sup (eSuc ` A)"
by(auto simp add: Sup_enat_def eSuc_Max inj_on_def dest: finite_imageD)
lemma sup_continuous_eSuc: "sup_continuous f ⟹ sup_continuous (λx. eSuc (f x))"
using eSuc_Sup [of "_ ` UNIV"] by (auto simp: sup_continuous_def image_comp)
subsection ‹Traditional theorem names›
lemmas enat_defs = zero_enat_def one_enat_def eSuc_def
plus_enat_def less_eq_enat_def less_enat_def
lemma iadd_is_0: "(m + n = (0::enat)) = (m = 0 ∧ n = 0)"
by (rule add_eq_0_iff_both_eq_0)
lemma i0_lb : "(0::enat) ≤ n"
by (rule zero_le)
lemma ile0_eq: "n ≤ (0::enat) ⟷ n = 0"
by (rule le_zero_eq)
lemma not_iless0: "¬ n < (0::enat)"
by (rule not_less_zero)
lemma i0_less[simp]: "(0::enat) < n ⟷ n ≠ 0"
by (rule zero_less_iff_neq_zero)
lemma imult_is_0: "((m::enat) * n = 0) = (m = 0 ∨ n = 0)"
by (rule mult_eq_0_iff)
end