(* Title: HOL/Library/Code_Target_Int.thy Author: Florian Haftmann, TU Muenchen *) section ‹Implementation of integer numbers by target-language integers› theory Code_Target_Int imports "../GCD" begin code_datatype int_of_integer declare [[code drop: integer_of_int]] context includes integer.lifting begin lemma [code]: "integer_of_int (int_of_integer k) = k" by transfer rule lemma [code]: "Int.Pos = int_of_integer ∘ integer_of_num" by transfer (simp add: fun_eq_iff) lemma [code]: "Int.Neg = int_of_integer ∘ uminus ∘ integer_of_num" by transfer (simp add: fun_eq_iff) lemma [code_abbrev]: "int_of_integer (numeral k) = Int.Pos k" by transfer simp lemma [code_abbrev]: "int_of_integer (- numeral k) = Int.Neg k" by transfer simp lemma [code, symmetric, code_post]: "0 = int_of_integer 0" by transfer simp lemma [code, symmetric, code_post]: "1 = int_of_integer 1" by transfer simp lemma [code_post]: "int_of_integer (- 1) = - 1" by simp lemma [code]: "k + l = int_of_integer (of_int k + of_int l)" by transfer simp lemma [code]: "- k = int_of_integer (- of_int k)" by transfer simp lemma [code]: "k - l = int_of_integer (of_int k - of_int l)" by transfer simp lemma [code]: "Int.dup k = int_of_integer (Code_Numeral.dup (of_int k))" by transfer simp declare [[code drop: Int.sub]] lemma [code]: "k * l = int_of_integer (of_int k * of_int l)" by simp lemma [code]: "k div l = int_of_integer (of_int k div of_int l)" by simp lemma [code]: "k mod l = int_of_integer (of_int k mod of_int l)" by simp lemma [code]: "divmod m n = map_prod int_of_integer int_of_integer (divmod m n)" unfolding prod_eq_iff divmod_def map_prod_def case_prod_beta fst_conv snd_conv by transfer simp lemma [code]: "HOL.equal k l = HOL.equal (of_int k :: integer) (of_int l)" by transfer (simp add: equal) lemma [code]: "k ≤ l ⟷ (of_int k :: integer) ≤ of_int l" by transfer rule lemma [code]: "k < l ⟷ (of_int k :: integer) < of_int l" by transfer rule lemma gcd_int_of_integer [code]: "gcd (int_of_integer x) (int_of_integer y) = int_of_integer (gcd x y)" by transfer rule lemma lcm_int_of_integer [code]: "lcm (int_of_integer x) (int_of_integer y) = int_of_integer (lcm x y)" by transfer rule end lemma (in ring_1) of_int_code_if: "of_int k = (if k = 0 then 0 else if k < 0 then - of_int (- k) else let l = 2 * of_int (k div 2); j = k mod 2 in if j = 0 then l else l + 1)" proof - from mod_div_equality have *: "of_int k = of_int (k div 2 * 2 + k mod 2)" by simp show ?thesis by (simp add: Let_def of_int_add [symmetric]) (simp add: * mult.commute) qed declare of_int_code_if [code] lemma [code]: "nat = nat_of_integer ∘ of_int" including integer.lifting by transfer (simp add: fun_eq_iff) code_identifier code_module Code_Target_Int ⇀ (SML) Arith and (OCaml) Arith and (Haskell) Arith end