Programming from zero

Higher-Order Functions and Lambdas Kotlin functions are first-class, which means programming from zero they can be stored in variables and data structures, passed as arguments to and returned from other higher-order functions. You can operate with functions in any way that is possible for other non-function values.

To facilitate this, Kotlin, as a statically typed programming language, uses a family of function types to represent functions and provides a set of specialized language constructs, such as lambda expressions. Higher-Order Functions A higher-order function is a function that takes functions as parameters, or returns a function. R, so it accepts a function that takes two arguments of types R and T and returns a value of type R. It is invoked inside the for-loop, and the return value is then assigned to accumulator. Lambdas are code blocks enclosed in curly braces.

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The following sections explain in more detail the concepts mentioned so far. These types have a special notation that corresponds to the signatures of the functions, i. C denotes a type that represents functions taking two arguments of types A and B and returning a value of type C. The Unit return type cannot be omitted. Function types can optionally have an additional receiver type, which is specified before a dot in the notation: the type A. C represents functions that can be called on a receiver object of A with a parameter of B and return a value of C. Function literals with receiver are often used along with these types.

These names can be used for documenting the meaning of the parameters. Function literals with receiver can be used as values of function types with receiver. Non-literal values of function types with and without receiver are interchangeable, so that the receiver can stand in for the first parameter, and vice versa. C can be passed or assigned where a A.