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## Class value_semantic

boost::program_options::value_semantic

## Synopsis

    class value_semantic {
    public:
      // construct/copy/destruct
      ~value_semantic();

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

## Description

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

### `value_semantic` public construct/copy/destruct

1.     ~value_semantic();

### `value_semantic` public member functions

1.     std::string name() const;

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

2.     unsigned min_tokens() const;

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

3.     unsigned max_tokens() const;

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

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

   Called when final value of an option is determined.