Книга: Standard Template Library Programmer
Adaptable Binary Function
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Adaptable Binary Function
Category: functors
Component type: concept
Description
An Adaptable Binary Function is a Binary Function with nested typedefs that define its argument types and result type. [1] [2] These nested typedefs make it possible to use function object adaptors.
Refinement of
Binary Function
Associated types
| First argument type | F::first_argument_type |
The type of F's first argument |
| Second argument type | F::second_argument_type |
The type of F's second argument |
| Result type | F::result_type |
The type returned when the Binary Function is called |
Notation
F A type that is a model of Binary Function
Valid expressions
None, except for those defined by Binary Function
Models
• plus
• project1st
• pointer_to_binary_function
Notes
[1] Note the implication of this: a function pointer T (*f)(X,Y) is a Binary Function, but not an Adaptable Binary Function: the expressions f::first_argument_type, f::second_argument_type, and f::result_type are nonsensical.
[2] When you define a class that is a model of Adaptable Binary Function, you must provide these typedefs. The easiest way to do this is to derive the class from the base class binary_function. This is an empty class, with no member functions or member variables; the only reason it exists is to make defining Adaptable Binary Functions more convenient. Binary_function is very similar to the base classes used by the iterator tag functions.
See also
Binary Function, Adaptable Generator, Adaptable Unary Function
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