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returns a function or value as its result. All other functions are first-order functions. In mathematics higher-order functions are also termed operators or functionals. The differential operator in calculus is a common example, since it maps a function to its derivative, also a function.
One way to do this is to say that two sets "have the same number of elements", if and only if all the elements of one set can be paired with the elements of the other, in such a way that each element is paired with exactly one element. Accordingly, one can define two sets to "have the same number of elements"—if there is a bijection between them.
For example, Python adds the feature that hash functions make use of a randomized seed that is generated once when the Python process starts in addition to the input to be hashed. [9] The Python hash is still a valid hash function when used within a single run, but if the values are persisted (for example, written to disk), they can no longer ...
In computer programming, an anonymous function (function literal, expression or block) is a function definition that is not bound to an identifier.Anonymous functions are often arguments being passed to higher-order functions or used for constructing the result of a higher-order function that needs to return a function. [1]
In Haskell, the polymorphic function map :: (a -> b) -> [a] -> [b] is generalized to a polytypic function fmap :: Functor f => (a -> b) -> f a -> f b, which applies to any type belonging the Functor type class. The type constructor of lists [] can be defined as an instance of the Functor type class using the map function from the previous example:
A multimap generalizes an associative array by allowing multiple values to be associated with a single key. [9] A bidirectional map is a related abstract data type in which the mappings operate in both directions: each value must be associated with a unique key, and a second lookup operation takes a value as an argument and looks up the key ...
The identity function on the positive integers is a completely multiplicative function (essentially multiplication by 1), considered in number theory. [8] In a metric space the identity function is trivially an isometry. An object without any symmetry has as its symmetry group the trivial group containing only this isometry (symmetry type C 1). [9]
represents the input set, which in this example is the set of natural numbers x 2 > 3 {\displaystyle x^{2}>3} is a predicate expression acting as a filter on members of the input set. 2 ⋅ x {\displaystyle 2\cdot x} is an output expression producing members of the new set from members of the input set that satisfy the predicate expression.