...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::program_options::value_semantic
// In header: <boost/program_options/value_semantic.hpp> class value_semantic { public: // construct/copy/destruct virtual ~value_semantic(); // public member functions virtual std::string name() const = 0; virtual unsigned min_tokens() const = 0; virtual unsigned max_tokens() const = 0; virtual bool is_composing() const = 0; virtual bool is_required() const = 0; virtual void parse(boost::any &, const std::vector< std::string > &, bool) const = 0; virtual bool apply_default(boost::any &) const = 0; virtual void notify(const boost::any &) const = 0; };
Class which specifies how the option's value is to be parsed and converted into C++ types.
value_semantic
public member functionsvirtual std::string name() const = 0;
Returns the name of the option. The name is only meaningful for automatic help message.
virtual unsigned min_tokens() const = 0;
The minimum number of tokens for this option that should be present on the command line.
virtual unsigned max_tokens() const = 0;
The maximum number of tokens for this option that should be present on the command line.
virtual bool is_composing() const = 0;
Returns true if values from different sources should be composed. Otherwise, value from the first source is used and values from other sources are discarded.
virtual bool is_required() const = 0;
Returns true if value must be given. Non-optional value
virtual void parse(boost::any & value_store, const std::vector< std::string > & new_tokens, bool utf8) const = 0;
Parses a group of tokens that specify a value of option. Stores the result in 'value_store', using whatever representation is desired. May be be called several times if value of the same option is specified more than once.
virtual bool apply_default(boost::any & value_store) const = 0;
Called to assign default value to 'value_store'. Returns true if default value is assigned, and false if no default value exists.
virtual void notify(const boost::any & value_store) const = 0;
Called when final value of an option is determined.