Monoid, group etc structures on M × N #
In this file we define one-binop (Monoid, Group etc) structures on M × N.
We also prove trivial simp lemmas, and define the following operations on MonoidHoms:
fst M N : M × N →* M,snd M N : M × N →* N: projectionsProd.fstandProd.sndasMonoidHoms;inl M N : M →* M × N,inr M N : N →* M × N: inclusions of first/second monoid into the product;f.prod g:M →* N × P: sendsxto(f x, g x);- When
Pis commutative,f.coprod g : M × N →* Psends(x, y)tof x * g y(without the commutativity assumption onP, seeMonoidHom.noncommPiCoprod); f.prodMap g : M × N → M' × N':Prod.map f gas aMonoidHom, sends(x, y)to(f x, g y).
Main declarations #
mulMulHom/mulMonoidHom: Multiplication bundled as a multiplicative/monoid homomorphism.divMonoidHom: Division bundled as a monoid homomorphism.
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Coproduct of two MulHoms with the same codomain:
f.coprod g (p : M × N) = f p.1 * g p.2.
(Commutative codomain; for the general case, see MulHom.noncommCoprod)
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Coproduct of two AddHoms with the same codomain:
f.coprod g (p : M × N) = f p.1 + g p.2.
(Commutative codomain; for the general case, see AddHom.noncommCoprod)
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Given monoids M, N, the natural projection homomorphism from M × N to M.
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Given additive monoids A, B, the natural projection homomorphism
from A × B to A
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Given monoids M, N, the natural projection homomorphism from M × N to N.
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Given additive monoids A, B, the natural projection homomorphism
from A × B to B
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Given monoids M, N, the natural inclusion homomorphism from M to M × N.
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Given additive monoids A, B, the natural inclusion homomorphism
from A to A × B.
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Given monoids M, N, the natural inclusion homomorphism from N to M × N.
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Given additive monoids A, B, the natural inclusion homomorphism
from B to A × B.
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Combine two MonoidHoms f : M →* N, g : M →* P into f.prod g : M →* N × P
given by (f.prod g) x = (f x, g x).
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Combine two AddMonoidHoms f : M →+ N, g : M →+ P into
f.prod g : M →+ N × P given by (f.prod g) x = (f x, g x)
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Prod.map as an AddMonoidHom.
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Coproduct of two MonoidHoms with the same codomain:
f.coprod g (p : M × N) = f p.1 * g p.2.
(Commutative case; for the general case, see MonoidHom.noncommCoprod.)
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Coproduct of two AddMonoidHoms with the same codomain:
f.coprod g (p : M × N) = f p.1 + g p.2.
(Commutative case; for the general case, see AddHom.noncommCoprod.)
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The equivalence between M × N and N × M given by swapping the components
is multiplicative.
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The equivalence between M × N and N × M given by swapping the
components is additive.
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The equivalence between (M × N) × P and M × (N × P) is multiplicative.
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The equivalence between (M × N) × P and M × (N × P) is additive.
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Four-way commutativity of Prod. The name matches mul_mul_mul_comm.
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Four-way commutativity of Prod.
The name matches mul_mul_mul_comm
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Product of multiplicative isomorphisms; the maps come from Equiv.prodCongr.
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Product of additive isomorphisms; the maps come from Equiv.prodCongr.
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Multiplying by the trivial monoid doesn't change the structure.
This is the MulEquiv version of Equiv.uniqueProd.
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Multiplying by the trivial monoid doesn't change the structure.
This is the AddEquiv version of Equiv.uniqueProd.
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Multiplying by the trivial monoid doesn't change the structure.
This is the MulEquiv version of Equiv.prodUnique.
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Multiplying by the trivial monoid doesn't change the structure.
This is the AddEquiv version of Equiv.prodUnique.
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The additive monoid equivalence between additive units of a product of two additive monoids, and the product of the additive units of each additive monoid.
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Multiplication and division as homomorphisms #
Multiplication as a monoid homomorphism.
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Addition as an additive monoid homomorphism.
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Division as a monoid homomorphism.
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Subtraction as an additive monoid homomorphism.