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Two objects that are not equal are said to be distinct. [4] Equality is often considered a kind of primitive notion, meaning, it is not formally defined, but rather informally said to be "a relation each thing bears to itself and nothing else". This characterization is notably circular ("nothing else"). This makes equality a somewhat slippery ...
Consider the two functions f and g mapping from and to natural numbers, defined as follows: To find f(n), first add 5 to n, then multiply by 2. To find g(n), first multiply n by 2, then add 10. These functions are extensionally equal; given the same input, both functions always produce the same value.
In mathematics, a relation denotes some kind of relationship between two objects in a set, which may or may not hold. [1] As an example, " is less than " is a relation on the set of natural numbers ; it holds, for instance, between the values 1 and 3 (denoted as 1 < 3 ), and likewise between 3 and 4 (denoted as 3 < 4 ), but not between the ...
In PHP, the triple equal sign, ===, denotes value and type equality, [8] meaning that not only do the two expressions evaluate to equal values, but they are also of the same data type. For instance, the expression 0 == false is true, but 0 === false is not, because the number 0 is an integer value whereas false is a Boolean value.
This is a binary operation whose value is true when its two arguments have the same value as each other. [4] Alternatively, in some texts ⇔ is used with this meaning, while ≡ is used for the higher-level metalogical notion of logical equivalence, according to which two formulas are logically equivalent when all models give them the same ...
It follows that, two ordered pairs (a,b) and (c,d) are equal if and only if a = c and b = d. Alternatively, an ordered pair can be formally thought of as a set {a,b} with a total order . (The notation ( a , b ) is also used to denote an open interval on the real number line , but the context should make it clear which meaning is intended.
Any two objects have a pair. The set {A,A} is abbreviated {A}, called the singleton containing A. Note that a singleton is a special case of a pair. Being able to construct a singleton is necessary, for example, to show the non-existence of the infinitely descending chains = {} from the Axiom of regularity.
Universal properties define objects uniquely up to a unique isomorphism. [1] Therefore, one strategy to prove that two objects are isomorphic is to show that they satisfy the same universal property. Universal constructions are functorial in nature: if one can carry out the construction for every object in a category C then one obtains a ...