Documentation

Mathlib.Algebra.Category.MonCat.Limits

The category of (commutative) (additive) monoids has all limits #

Further, these limits are preserved by the forgetful functor --- that is, the underlying types are just the limits in the category of types.

@[reducible, inline]
abbrev MonCatMax :
Type ((max u1 u2) + 1)

An alias for MonCat.{max u v}, to deal around unification issues.

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    @[reducible, inline]
    abbrev AddMonCatMax :
    Type ((max u1 u2) + 1)

    An alias for AddMonCat.{max u v}, to deal around unification issues.

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      The flat sections of a functor into MonCat form a submonoid of all sections.

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        The flat sections of a functor into AddMonCat form an additive submonoid of all sections.

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          limit.π (F ⋙ forget MonCat) j as a MonoidHom.

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            limit.π (F ⋙ forget AddMonCat) j as an AddMonoidHom.

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              Construction of a limit cone in MonCat. (Internal use only; use the limits API.)

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                (Internal use only; use the limits API.)

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                  Witness that the limit cone in MonCat is a limit cone. (Internal use only; use the limits API.)

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                    (Internal use only; use the limits API.)

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                      If (F ⋙ forget MonCat).sections is u-small, F has a limit.

                      If (F ⋙ forget AddMonCat).sections is u-small, F has a limit.

                      If J is u-small, the forgetful functor from MonCat.{u} preserves limits of shape J.

                      If J is u-small, the forgetful functor from AddMonCat.{u}

                      preserves limits of shape J.

                      The forgetful functor from monoids to types preserves all limits.

                      This means the underlying type of a limit can be computed as a limit in the category of types.

                      The forgetful functor from additive monoids to types preserves all limits.

                      This means the underlying type of a limit can be computed as a limit in the category of types.

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                      The forgetful functor from monoids to types preserves all limits.

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                      The forgetful functor from additive monoids to types preserves all limits.

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                      @[reducible, inline]
                      abbrev CommMonCatMax :
                      Type ((max u1 u2) + 1)

                      An alias for CommMonCat.{max u v}, to deal around unification issues.

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                        @[reducible, inline]
                        abbrev AddCommMonCatMax :
                        Type ((max u1 u2) + 1)

                        An alias for AddCommMonCat.{max u v}, to deal around unification issues.

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                          We show that the forgetful functor CommMonCatMonCat creates limits.

                          All we need to do is notice that the limit point has a CommMonoid instance available, and then reuse the existing limit.

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                          We show that the forgetful functor AddCommMonCatAddMonCat creates limits.

                          All we need to do is notice that the limit point has an AddCommMonoid instance available,

                          and then reuse the existing limit.

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                          A choice of limit cone for a functor into CommMonCat. (Generally, you'll just want to use limit F.)

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                            If (F ⋙ forget CommMonCat).sections is u-small, F has a limit.

                            If (F ⋙ forget AddCommMonCat).sections is u-small, F has a limit.

                            If J is u-small, CommMonCat.{u} has limits of shape J.

                            If J is u-small, AddCommMonCat.{u} has limits of shape J.

                            The forgetful functor from commutative monoids to monoids preserves all limits.

                            This means the underlying type of a limit can be computed as a limit in the category of monoids.

                            The forgetful functor from additive commutative monoids to additive monoids preserves all limits.

                            This means the underlying type of a limit can be computed as a limit in the category of additive

                            monoids.

                            If J is u-small, the forgetful functor from CommMonCat.{u} preserves limits of shape J.

                            If J is u-small, the forgetful functor from AddCommMonCat.{u}

                            preserves limits of shape J.

                            The forgetful functor from commutative monoids to types preserves all limits.

                            This means the underlying type of a limit can be computed as a limit in the category of types.

                            The forgetful functor from additive commutative monoids to types preserves all

                            limits.

                            This means the underlying type of a limit can be computed as a limit in the category of types.

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                            The forgetful functor from commutative monoids to types preserves all limits.

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                            The forgetful functor from commutative additive monoids to types preserves all limits.

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