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For example, in C, int const x = 1; declares an object x of int const type – the const is part of the type, as if it were parsed "(int const) x" – while in Ada, X: constant INTEGER:= 1_ declares a constant (a kind of object) X of INTEGER type: the constant is part of the object, but not part of the type. This has two subtle results.
In category theory, the product of two (or more) objects in a category is a notion designed to capture the essence behind constructions in other areas of mathematics such as the Cartesian product of sets, the direct product of groups or rings, and the product of topological spaces.
Conversely, the mutable keyword allows a class member to be changed even if an object was instantiated as const. Even functions can be const in C++. The meaning here is that only a const function may be called for an object instantiated as const; a const function doesn't change any non-mutable data. C# has both a const and a readonly qualifier ...
Copy constructors are the standard way of copying objects in C++, as opposed to cloning, and have C++-specific nuances. The first argument of such a constructor is a reference to an object of the same type as is being constructed (const or non-const), which might be followed by parameters of any type (all having default values).
The coproduct of a family of objects is essentially the "least specific" object to which each object in the family admits a morphism. It is the category-theoretic dual notion to the categorical product, which means the definition is the same as the product but with all arrows reversed. Despite this seemingly innocuous change in the name and ...
Any two objects Y and Z of C have an exponential Z Y in C. The first two conditions can be combined to the single requirement that any finite (possibly empty) family of objects of C admit a product in C , because of the natural associativity of the categorical product and because the empty product in a category is the terminal object of that ...
For small categories, this is the same as the action on objects of the categorical product in the category Cat. A functor whose domain is a product category is known as a bifunctor. An important example is the Hom functor, which has the product of the opposite of some category with the original category as domain: Hom : C op × C → Set.
The same distinction holds for comparing objects for equality: most basically there is a difference between identity (same object) and equality (same value), corresponding to shallow equality and (1 level) deep equality of two object references, but then further whether equality means comparing only the fields of the object in question or ...