variant-o.hpp File Reference

This file defines a simple alternative to boost::variant. More...

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Description

This file defines a simple alternative to boost::variant.

It pulls in fewer headers and has a shorter code path, but also doesn't deal with alignment issues and is not threadsafe.

Values can be stored using operator= . In order to access the value stored in lib::VariantO, you additionally need to define an access "functor"

• with a typedef "Ret" for the return type

• providing a static Ret access(ELM&) function for each of the types used in the VariantO "The" typical example for such an access "functor" is the util::AccessCasted template.

  Deprecated:

  immature first try. Preferably use lib::Variant

  Todo:

  the instance handling for the accessor seems somewhat clumsy: we're creating a static accessor instance for each type of access functor, and each of these accessors holds a trampoline table. Why are we building a table, while we're using a templated access functor anyway? This table inhibits inlining, and there seems to be no runtime benefit. This whole design indeed was a hastily made (prompted by actual need) first attempt. It should be rewritten from scratch (HIV 4/2015)

  ///////////////////////////////////////TICKET #738 should be rewritten from scratch

  ///////////////////////////////////////TICKET #141 write an unit test for variant

  See also

  wrapperptr.hpp usage example

Definition in file variant-o.hpp.

#include "lib/meta/typelist-util.hpp"
#include "lib/meta/generator.hpp"
#include "lib/nocopy.hpp"

Namespaces
namespace	lib
	Implementation namespace for support and library code.
namespace	lib::variant

Classes
struct	Holder< TYPES >
	internal helper used to build a variant storage wrapper. More...
struct	Holder< TYPES >::Buffer
	Storage to hold the actual value. More...
struct	Holder< TYPES >::PlacementAdapter< T, BASE, idx >
struct	Holder< TYPES >::CaseSelect< FUNCTOR >
	provide a dispatcher table based visitation mechanism More...
struct	Holder< TYPES >::CasePrepare< T, BASE, i >
	initialise the dispatcher (trampoline) for the case of accessing type T More...
struct	Holder< TYPES >::Deleter
class	VariantO< TYPES, Access >
	A variant wrapper (typesafe union) capable of holding a value of any of a bounded collection of types. More...