header {* Numeral Syntax for Types *}
theory Numeral_Type
imports Cardinality
begin
subsection {* Numeral Types *}
typedef (open) num0 = "UNIV :: nat set" ..
typedef (open) num1 = "UNIV :: unit set" ..
typedef (open) 'a bit0 = "{0 ..< 2 * int CARD('a::finite)}"
proof
show "0 ∈ {0 ..< 2 * int CARD('a)}"
by simp
qed
typedef (open) 'a bit1 = "{0 ..< 1 + 2 * int CARD('a::finite)}"
proof
show "0 ∈ {0 ..< 1 + 2 * int CARD('a)}"
by simp
qed
lemma card_num0 [simp]: "CARD (num0) = 0"
unfolding type_definition.card [OF type_definition_num0]
by simp
lemma card_num1 [simp]: "CARD(num1) = 1"
unfolding type_definition.card [OF type_definition_num1]
by (simp only: card_unit)
lemma card_bit0 [simp]: "CARD('a bit0) = 2 * CARD('a::finite)"
unfolding type_definition.card [OF type_definition_bit0]
by simp
lemma card_bit1 [simp]: "CARD('a bit1) = Suc (2 * CARD('a::finite))"
unfolding type_definition.card [OF type_definition_bit1]
by simp
instance num1 :: finite
proof
show "finite (UNIV::num1 set)"
unfolding type_definition.univ [OF type_definition_num1]
using finite by (rule finite_imageI)
qed
instance bit0 :: (finite) card2
proof
show "finite (UNIV::'a bit0 set)"
unfolding type_definition.univ [OF type_definition_bit0]
by simp
show "2 ≤ CARD('a bit0)"
by simp
qed
instance bit1 :: (finite) card2
proof
show "finite (UNIV::'a bit1 set)"
unfolding type_definition.univ [OF type_definition_bit1]
by simp
show "2 ≤ CARD('a bit1)"
by simp
qed
subsection {* Locales for for modular arithmetic subtypes *}
locale mod_type =
fixes n :: int
and Rep :: "'a::{zero,one,plus,times,uminus,minus} => int"
and Abs :: "int => 'a::{zero,one,plus,times,uminus,minus}"
assumes type: "type_definition Rep Abs {0..<n}"
and size1: "1 < n"
and zero_def: "0 = Abs 0"
and one_def: "1 = Abs 1"
and add_def: "x + y = Abs ((Rep x + Rep y) mod n)"
and mult_def: "x * y = Abs ((Rep x * Rep y) mod n)"
and diff_def: "x - y = Abs ((Rep x - Rep y) mod n)"
and minus_def: "- x = Abs ((- Rep x) mod n)"
begin
lemma size0: "0 < n"
using size1 by simp
lemmas definitions =
zero_def one_def add_def mult_def minus_def diff_def
lemma Rep_less_n: "Rep x < n"
by (rule type_definition.Rep [OF type, simplified, THEN conjunct2])
lemma Rep_le_n: "Rep x ≤ n"
by (rule Rep_less_n [THEN order_less_imp_le])
lemma Rep_inject_sym: "x = y <-> Rep x = Rep y"
by (rule type_definition.Rep_inject [OF type, symmetric])
lemma Rep_inverse: "Abs (Rep x) = x"
by (rule type_definition.Rep_inverse [OF type])
lemma Abs_inverse: "m ∈ {0..<n} ==> Rep (Abs m) = m"
by (rule type_definition.Abs_inverse [OF type])
lemma Rep_Abs_mod: "Rep (Abs (m mod n)) = m mod n"
by (simp add: Abs_inverse pos_mod_conj [OF size0])
lemma Rep_Abs_0: "Rep (Abs 0) = 0"
by (simp add: Abs_inverse size0)
lemma Rep_0: "Rep 0 = 0"
by (simp add: zero_def Rep_Abs_0)
lemma Rep_Abs_1: "Rep (Abs 1) = 1"
by (simp add: Abs_inverse size1)
lemma Rep_1: "Rep 1 = 1"
by (simp add: one_def Rep_Abs_1)
lemma Rep_mod: "Rep x mod n = Rep x"
apply (rule_tac x=x in type_definition.Abs_cases [OF type])
apply (simp add: type_definition.Abs_inverse [OF type])
apply (simp add: mod_pos_pos_trivial)
done
lemmas Rep_simps =
Rep_inject_sym Rep_inverse Rep_Abs_mod Rep_mod Rep_Abs_0 Rep_Abs_1
lemma comm_ring_1: "OFCLASS('a, comm_ring_1_class)"
apply (intro_classes, unfold definitions)
apply (simp_all add: Rep_simps zmod_simps field_simps)
done
end
locale mod_ring = mod_type +
constrains n :: int
and Rep :: "'a::{number_ring} => int"
and Abs :: "int => 'a::{number_ring}"
begin
lemma of_nat_eq: "of_nat k = Abs (int k mod n)"
apply (induct k)
apply (simp add: zero_def)
apply (simp add: Rep_simps add_def one_def zmod_simps add_ac)
done
lemma of_int_eq: "of_int z = Abs (z mod n)"
apply (cases z rule: int_diff_cases)
apply (simp add: Rep_simps of_nat_eq diff_def zmod_simps)
done
lemma Rep_number_of:
"Rep (number_of w) = number_of w mod n"
by (simp add: number_of_eq of_int_eq Rep_Abs_mod)
lemma iszero_number_of:
"iszero (number_of w::'a) <-> number_of w mod n = 0"
by (simp add: Rep_simps number_of_eq of_int_eq iszero_def zero_def)
lemma cases:
assumes 1: "!!z. [|(x::'a) = of_int z; 0 ≤ z; z < n|] ==> P"
shows "P"
apply (cases x rule: type_definition.Abs_cases [OF type])
apply (rule_tac z="y" in 1)
apply (simp_all add: of_int_eq mod_pos_pos_trivial)
done
lemma induct:
"(!!z. [|0 ≤ z; z < n|] ==> P (of_int z)) ==> P (x::'a)"
by (cases x rule: cases) simp
end
subsection {* Number ring instances *}
text {*
Unfortunately a number ring instance is not possible for
@{typ num1}, since 0 and 1 are not distinct.
*}
instantiation num1 :: "{comm_ring,comm_monoid_mult,number}"
begin
lemma num1_eq_iff: "(x::num1) = (y::num1) <-> True"
by (induct x, induct y) simp
instance proof
qed (simp_all add: num1_eq_iff)
end
instantiation
bit0 and bit1 :: (finite) "{zero,one,plus,times,uminus,minus}"
begin
definition Abs_bit0' :: "int => 'a bit0" where
"Abs_bit0' x = Abs_bit0 (x mod int CARD('a bit0))"
definition Abs_bit1' :: "int => 'a bit1" where
"Abs_bit1' x = Abs_bit1 (x mod int CARD('a bit1))"
definition "0 = Abs_bit0 0"
definition "1 = Abs_bit0 1"
definition "x + y = Abs_bit0' (Rep_bit0 x + Rep_bit0 y)"
definition "x * y = Abs_bit0' (Rep_bit0 x * Rep_bit0 y)"
definition "x - y = Abs_bit0' (Rep_bit0 x - Rep_bit0 y)"
definition "- x = Abs_bit0' (- Rep_bit0 x)"
definition "0 = Abs_bit1 0"
definition "1 = Abs_bit1 1"
definition "x + y = Abs_bit1' (Rep_bit1 x + Rep_bit1 y)"
definition "x * y = Abs_bit1' (Rep_bit1 x * Rep_bit1 y)"
definition "x - y = Abs_bit1' (Rep_bit1 x - Rep_bit1 y)"
definition "- x = Abs_bit1' (- Rep_bit1 x)"
instance ..
end
interpretation bit0:
mod_type "int CARD('a::finite bit0)"
"Rep_bit0 :: 'a::finite bit0 => int"
"Abs_bit0 :: int => 'a::finite bit0"
apply (rule mod_type.intro)
apply (simp add: int_mult type_definition_bit0)
apply (rule one_less_int_card)
apply (rule zero_bit0_def)
apply (rule one_bit0_def)
apply (rule plus_bit0_def [unfolded Abs_bit0'_def])
apply (rule times_bit0_def [unfolded Abs_bit0'_def])
apply (rule minus_bit0_def [unfolded Abs_bit0'_def])
apply (rule uminus_bit0_def [unfolded Abs_bit0'_def])
done
interpretation bit1:
mod_type "int CARD('a::finite bit1)"
"Rep_bit1 :: 'a::finite bit1 => int"
"Abs_bit1 :: int => 'a::finite bit1"
apply (rule mod_type.intro)
apply (simp add: int_mult type_definition_bit1)
apply (rule one_less_int_card)
apply (rule zero_bit1_def)
apply (rule one_bit1_def)
apply (rule plus_bit1_def [unfolded Abs_bit1'_def])
apply (rule times_bit1_def [unfolded Abs_bit1'_def])
apply (rule minus_bit1_def [unfolded Abs_bit1'_def])
apply (rule uminus_bit1_def [unfolded Abs_bit1'_def])
done
instance bit0 :: (finite) comm_ring_1
by (rule bit0.comm_ring_1)+
instance bit1 :: (finite) comm_ring_1
by (rule bit1.comm_ring_1)+
instantiation bit0 and bit1 :: (finite) number_ring
begin
definition "(number_of w :: _ bit0) = of_int w"
definition "(number_of w :: _ bit1) = of_int w"
instance proof
qed (rule number_of_bit0_def number_of_bit1_def)+
end
interpretation bit0:
mod_ring "int CARD('a::finite bit0)"
"Rep_bit0 :: 'a::finite bit0 => int"
"Abs_bit0 :: int => 'a::finite bit0"
..
interpretation bit1:
mod_ring "int CARD('a::finite bit1)"
"Rep_bit1 :: 'a::finite bit1 => int"
"Abs_bit1 :: int => 'a::finite bit1"
..
text {* Set up cases, induction, and arithmetic *}
lemmas bit0_cases [case_names of_int, cases type: bit0] = bit0.cases
lemmas bit1_cases [case_names of_int, cases type: bit1] = bit1.cases
lemmas bit0_induct [case_names of_int, induct type: bit0] = bit0.induct
lemmas bit1_induct [case_names of_int, induct type: bit1] = bit1.induct
lemmas bit0_iszero_number_of [simp] = bit0.iszero_number_of
lemmas bit1_iszero_number_of [simp] = bit1.iszero_number_of
subsection {* Syntax *}
syntax
"_NumeralType" :: "num_const => type" ("_")
"_NumeralType0" :: type ("0")
"_NumeralType1" :: type ("1")
translations
(type) "1" == (type) "num1"
(type) "0" == (type) "num0"
parse_translation {*
let
fun mk_bintype n =
let
fun mk_bit 0 = Syntax.const @{type_syntax bit0}
| mk_bit 1 = Syntax.const @{type_syntax bit1};
fun bin_of n =
if n = 1 then Syntax.const @{type_syntax num1}
else if n = 0 then Syntax.const @{type_syntax num0}
else if n = ~1 then raise TERM ("negative type numeral", [])
else
let val (q, r) = Integer.div_mod n 2;
in mk_bit r $ bin_of q end;
in bin_of n end;
fun numeral_tr (*"_NumeralType"*) [Const (str, _)] =
mk_bintype (the (Int.fromString str))
| numeral_tr (*"_NumeralType"*) ts = raise TERM ("numeral_tr", ts);
in [(@{syntax_const "_NumeralType"}, numeral_tr)] end;
*}
print_translation {*
let
fun int_of [] = 0
| int_of (b :: bs) = b + 2 * int_of bs;
fun bin_of (Const (@{type_syntax num0}, _)) = []
| bin_of (Const (@{type_syntax num1}, _)) = [1]
| bin_of (Const (@{type_syntax bit0}, _) $ bs) = 0 :: bin_of bs
| bin_of (Const (@{type_syntax bit1}, _) $ bs) = 1 :: bin_of bs
| bin_of t = raise TERM ("bin_of", [t]);
fun bit_tr' b [t] =
let
val rev_digs = b :: bin_of t handle TERM _ => raise Match
val i = int_of rev_digs;
val num = string_of_int (abs i);
in
Syntax.const @{syntax_const "_NumeralType"} $ Syntax.free num
end
| bit_tr' b _ = raise Match;
in [(@{type_syntax bit0}, bit_tr' 0), (@{type_syntax bit1}, bit_tr' 1)] end;
*}
subsection {* Examples *}
lemma "CARD(0) = 0" by simp
lemma "CARD(17) = 17" by simp
lemma "8 * 11 ^ 3 - 6 = (2::5)" by simp
end