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

This is the documentation for an old version of Boost. Click here to view this page for the latest version.

Class value_semantic

boost::program_options::value_semantic —


class value_semantic {
// construct/copy/destruct

// public member functions
virtual std::string name() const;
virtual unsigned min_tokens() const;
virtual unsigned max_tokens() const;
virtual bool is_composing() const;
virtual void 
parse(boost::any &, const std::vector< std::string > &, bool) const;
virtual bool apply_default(boost::any &) const;
virtual void notify(const boost::any &) const;


Class which specifies how the option's value is to be parsed and converted into C++ types.

value_semantic construct/copy/destruct

  1. ~value_semantic();

value_semantic public member functions

  1. virtual std::string name() const;

    Returns the name of the option. The name is only meaningful for automatic help message.

  2. virtual unsigned min_tokens() const;

    The minimum number of tokens for this option that should be present on the command line.

  3. virtual unsigned max_tokens() const;

    The maximum number of tokens for this option that should be present on the command line.

  4. virtual bool is_composing() const;

    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.

  5. virtual void 
    parse(boost::any & value_store, const std::vector< std::string > & new_tokens, 
    bool utf8) const;

    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.

  6. virtual bool apply_default(boost::any & value_store) const;

    Called to assign default value to 'value_store'. Returns true if default value is assigned, and false if no default value exists.

  7. virtual void notify(const boost::any & value_store) const;

    Called when final value of an option is determined.

Copyright 2002-2004 Vladimir Prus