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A higher-order function is a function that takes a function as an argument or returns one as a result. This is commonly used to customize the behavior of a generically defined function, often a looping construct or recursion scheme. Anonymous functions are a convenient way to specify such function arguments. The following examples are in Python 3.
Python's limited support for anonymous functions is the lambda construct. An example is the anonymous function which squares its input, called with the argument of 5: An example is the anonymous function which squares its input, called with the argument of 5:
This property is inherited from lambda calculus, where multi-argument functions are usually represented in curried form. Currying is related to, but not the same as partial application . [ 1 ] [ 2 ] In practice, the programming technique of closures can be used to perform partial application and a kind of currying, by hiding arguments in an ...
The term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).
Anonymous recursion is primarily of use in allowing recursion for anonymous functions, particularly when they form closures or are used as callbacks, to avoid having to bind the name of the function.
In this Erlang example, the higher-order function or_else/2 takes a list of functions (Fs) and argument (X). It evaluates the function F with the argument X as argument. If the function F returns false then the next function in Fs will be evaluated. If the function F returns {false, Y} then the next function in Fs with argument Y will be
It is usually instantiated with, or borrowed from, models of computation such as lambda calculus which make heavy use of higher-order functions. A programming language can be considered higher-order if components, such as procedures or labels, can be used just like data. For example, these elements could be used in the same way as arguments or ...
C++ also allows objects to provide an implementation of the function call operation. The Standard Template Library accepts these objects (called functors) as parameters. Many dynamic languages, such as JavaScript, Lua, Python, Perl [1] [2] and PHP, allow a function object to be passed.