Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

LvaluePropertyMap

The LvaluePropertyMap provides operator[] and function get() for accessing a reference to a value object. The return type refines that of function get()in ReadablePropertyMap; it can only be a reference (for a mutable LvaluePropertyMap) or a const reference (for a non-mutable LvaluePropertyMap).

Refinement of

ReadablePropertyMap for non-mutable or ReadWritePropertyMap for mutable property map.

Notation

`PMap`	A type that is a model of LvaluePropertyMap.
`pmap`	An object of type `PMap`.
`key`	An object of type `boost::property_traits<PMap>::key_type`.

Associated Types

Reference Type	`boost::property_traits<PMap>::reference`	The reference type, which must be a reference or const reference to the value type of the property map.
Property Map Category	`boost::property_traits<PMap>::category`	The category of the property: a type convertible to `boost::lvalue_property_map_tag`.

Valid Expressions

Name	Expression	Return Type	Description
Access Property Value	`pmap[key]`	`value_type&` for mutable, `const value_type&` otherwise.	Obtain a reference to the value associated with `key`.

Concept Checking Class

  template <class PMap, class Key>
  struct LvaluePropertyMapConcept
  {
    typedef typename property_traits<PMap>::category Category;
    typedef boost::lvalue_property_map_tag LvalueTag;
    typedef const typename property_traits<PMap>::value_type& const_reference;
    void constraints() {
      function_requires< ReadWritePropertyMapConcept<PMap, Key> >();
      function_requires< ConvertibleConcept<Category, LvalueTag> >();

      const_reference ref = pmap[k];
    }
    PMap pmap;
    Key k;
  };

  template <class PMap, class Key>
  struct Mutable_LvaluePropertyMapConcept
  {
    typedef typename property_traits<PMap>::category Category;
    typedef boost::lvalue_property_map_tag LvalueTag;
    typedef typename property_traits<PMap>::value_type& reference;
    void constraints() { 
      function_requires< ReadWritePropertyMapConcept<PMap, Key> >();
      function_requires<ConvertibleConcept<Category, LvalueTag> >();

      reference ref = pmap[k];
    }
    PMap pmap;
    Key k;
  };