108 lines
3 KiB
Text
108 lines
3 KiB
Text
import macros
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---
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--- Classes of structures, and axiomatic classes of structures
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---
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--- A "structure" consists of a carrier, and some data (whose type depends on the carrier)
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definition StructClass : (Type 1) := Type → Type -- the type of the data
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definition structure (S : StructClass) : (Type 1)
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:= sig T : Type, S T
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definition carrier {S : StructClass} (M : structure S) : Type
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:= proj1 M
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definition data {S : StructClass} (M : structure S) : S (carrier M)
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:= proj2 M
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--- An "axiomatic class" is a class of structures satisfying some predicate (the "axioms")
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definition AxClass : (Type 1)
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:= sig S : StructClass, structure S → Bool
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-- Coercion from AxClass to StructClass
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definition struct_class (C : AxClass) : StructClass
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:= proj1 C
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definition axioms {C : AxClass} (M : structure (struct_class C))
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:= proj2 C M
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definition instance (C : AxClass) : (Type 1)
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:= sig M : structure (struct_class C), axioms M
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definition struct {C : AxClass} (M : instance C)
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:= proj1 M
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definition hyps {C : AxClass} (M : instance C) : axioms (struct M)
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:= proj2 M
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---
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--- Examples
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---
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--- multiplication (for overloading *)
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definition MulStruct : StructClass
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:= λ T, T → T → T
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definition mul {M : structure MulStruct} (x y : carrier M) : carrier M
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:= data M x y
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infixl 70 * : mul
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definition mul_is_assoc (M : structure MulStruct) : Bool
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:= ∀ x y z : carrier M, (x * y) * z = x * (y * z)
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definition mul_is_comm (M : structure MulStruct) : Bool
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:= ∀ x y z : carrier M, x * y = y * x
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--- semigroups
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definition Semigroup : AxClass
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:= pair MulStruct mul_is_assoc
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--- to fill the hole above automatically
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theorem semigroup_mul_is_assoc (M : instance Semigroup) : mul_is_assoc (struct M)
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:= hyps M
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definition OneStruct : StructClass
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:= λ T, T
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definition one {M : structure OneStruct} : carrier M
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:= data M
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-- structures with mult and one
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definition MonoidStruct : StructClass
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:= λ T, OneStruct T # MulStruct T
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definition MonoidStruct_to_OneStruct (M : structure MonoidStruct) : (structure OneStruct)
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:= pair (carrier M) (proj1 (data M))
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definition MonoidStruct_to_MulStruct (M : structure MonoidStruct) : (structure MulStruct)
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:= pair (carrier M) (proj2 (data M))
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variable M : structure MonoidStruct
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check carrier M = carrier (MonoidStruct_to_OneStruct M)
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theorem test1 (M : structure MonoidStruct) : carrier M = carrier (MonoidStruct_to_OneStruct M)
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:= refl (carrier M)
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definition is_mul_right_id (M : structure MonoidStruct) : Bool
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:= let m : carrier M → carrier M → carrier M := @mul (MonoidStruct_to_MulStruct M),
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o : carrier M := @one (MonoidStruct_to_OneStruct M)
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in ∀ x : carrier M, m x o = x
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definition is_monoid (M : structure MonoidStruct) : Bool
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:= mul_is_assoc (MonoidStruct_to_MulStruct M) ∧ is_mul_right_id M
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definition Monoid : AxClass
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:= pair MonoidStruct is_monoid
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theorem monoid_is_mul_right_id (M : instance Monoid) : is_mul_right_id (struct M)
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:= and_elimr (proj2 M)
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theorem monoid_mul_is_assoc (M : instance Monoid) : mul_is_assoc (MonoidStruct_to_MulStruct (struct M))
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:= and_eliml (proj2 M)
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