lens.hpp File Reference

Lenses are proxy objects that allow a value to be accessed and mutated via a pair of functions ("get" and "put"). More...

#include <type_traits>
#include <utility>

Classes
struct	cal::lens_base< Lens, T >
	CRTP base type for constructing Lens types. More...
struct	cal::lens_traits< Lens >
	Traits class for the Lens concept. More...
struct	cal::negating_lens< Lens, T >
	A lens that negates the value before storing or accessing it. More...
struct	cal::scaling_lens< Lens, Factor, T >
	A lens that scales the value by a factor before storing or accessing it. More...

Namespaces
	cal
	Primary namespace.

Functions
template<class T >
negating_lens< T >	cal::make_negating_lens (T &&x)
	Constructs a negating_lens from a given value.
template<class T , class U >
scaling_lens< T, U >	cal::make_scaling_lens (T &&lens, U &&factor)
	Constructs a scaling_lens from a given value.

Detailed Description

Lenses are proxy objects that allow a value to be accessed and mutated via a pair of functions ("get" and "put").

The concept is named after the Haskell lens package. Lenses are not required to be Copyable, only Movable. They must allow the following operations:

// This is the "get" function ("getter").
operator Lens::value_type() const;

// This is the "put" function ("setter").
Lens& operator=(const Lens::value_type& x);

// This is the rvalue-version of the "put" function (optional).
Lens& operator=(T&& x);