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## Class any

boost::any — A class whose instances can hold instances of any type that satisfies ValueType requirements.

## Synopsis

    class any {
    public:
      // construct/copy/destruct
      any();
      any(const any &);
      template<typename ValueType> any(const ValueType &);
      any & operator=(const any &);
      template<typename ValueType> any & operator=(const ValueType &);
      ~any();

      // modifiers
      any & swap(any &);

      // queries
      bool empty() const;
      const std::type_info & type() const;
    };

## Description

### `any` construct/copy/destruct

1.     any();

   Postconditions: | `this->empty()`

2.     any(const any & other);

   Effects: | Copy constructor that copies content of `other` into new instance, so that any content is equivalent in both type and value to the content of `other`, or empty if `other` is empty.
   Throws: | May fail with a `std::bad_alloc` exception or any exceptions arising from the copy constructor of the contained type.

3.     template<typename ValueType> any(const ValueType & value);

   Effects: | Makes a copy of `value`, so that the initial content of the new instance is equivalent in both type and value to `value`.
   Throws: | `std::bad_alloc` or any exceptions arising from the copy constructor of the contained type.

4.     any & operator=(const any & rhs);

   Effects: | Copies content of `rhs` into current instance, discarding previous content, so that the new content is equivalent in both type and value to the content of `rhs`, or empty if `rhs.empty()`.
   Throws: | `std::bad_alloc` or any exceptions arising from the copy constructor of the contained type. Assignment satisfies the strong guarantee of exception safety.

5.     template<typename ValueType> any & operator=(const ValueType & rhs);

   Effects: | Makes a copy of `rhs`, discarding previous content, so that the new content of is equivalent in both type and value to `rhs`.
   Throws: | `std::bad_alloc` or any exceptions arising from the copy constructor of the contained type. Assignment satisfies the strong guarantee of exception safety.

6.     ~any();

   Effects: | Releases any and all resources used in management of instance.
   Throws: | Nothing.

### `any` modifiers

1.     any & swap(any & rhs);

   Effects: | Exchange of the contents of `*this` and `rhs`.
   Returns: | `*this`
   Throws: | Nothing.

### `any` queries

1.     bool empty() const;

   Returns: | `true` if instance is empty, otherwise `false`.
   Throws: | Will not throw.

2.     const std::type_info & type() const;

   Returns: | the `typeid` of the contained value if instance is non-empty, otherwise `typeid(void)`.
   Notes: | Useful for querying against types known either at compile time or only at runtime.

| Copyright © 2001 Kevlin Henney