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Category : functors Component type: concept


A Unary Function is a kind of functors : an object that is called as if it were an ordinary C++ function. A Unary Function is called with a single argument.

Refinement of


Associated types

Argument type The type of the Unary Function's argument.
Result type The type returned when the Unary Function is called


F A type that is a model of Unary Function
X The argument type of F
Result The result type of F
f Object of type F
x Object of type X


The domain of a Unary Function is the set of all permissible values for its argument.

The range of a Unary Function is the set of all possible values that it may return.

Valid expressions

Name Expression Type requirements Return type
Function call f(x)   Result

Expression semantics

Name Expression Precondition Semantics Postcondition
Function call f(x) x is in f's domain Calls f with x as an argument, and returns a value of type Result [1] The return value is in f's range

Complexity guarantees



  • Result (*)(X)


[1] Two different invocations of f may return different results, even if f is called with the same arguments both times. A Unary Function may refer to local state, perform I/O, and so on. The expression f(x) is permitted to change f's state.

See also

functors, Generator, BinaryFunction AdaptableUnaryFunction

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