transform_view

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### transform_view

The unary version of `transform_view` presents a view of its underlying sequence given a unary function object or function pointer. The binary version of `transform_view` presents a view of 2 underlying sequences, given a binary function object or function pointer. The `transform_view` inherits the traversal characteristics (see Sequence Traversal Concept) of its underlying sequence or sequences.

##### Header

    #include <boost/fusion/view/transform_view.hpp>
    #include <boost/fusion/include/transform_view.hpp>

##### Synopsis

Unary Version

    template <typename Sequence, typename F1>
    struct transform_view;

Binary Version

    template <typename Sequence1, typename Sequence2, typename F2>
    struct transform_view;

##### Template parameters

Parameter | Description | Default
--- | --- | ---
`Sequence` | A Forward Sequence |
`Sequence1` | A Forward Sequence |
`Sequence2` | A Forward Sequence |
`F1` | A unary function object or function pointer. ``boost::result_of`<F1(E)>::type` is the return type of an instance of `F1` when called with a value of each element type `E` in the input sequence. |
`F2` | A binary function object or function pointer. ``boost::result_of`<F2(E1, E2)>::type` is the return type of an instance of `F2` when called with a value of each corresponding pair of element type `E1` and `E2` in the input sequences. |

##### Model of

- Forward Sequence, Bidirectional Sequence or Random Access Sequence depending on the traversal characteristics (see Sequence Traversal Concept) of its underlying sequence.

Notation

`TV`

  A `transform_view` type

`BTV`

  A binary `transform_view` type

`UTV`

  A unary `transform_view` type

`f1`

  An instance of `F1`

`f2`

  An instance of `F2`

`s`

  An instance of `Sequence`

`s1`

  An instance of `Sequence1`

`s2`

  An instance of `Sequence2`

`tv`, `tv2`

  Instances of `transform_view`

##### Expression Semantics

Semantics of an expression is defined only where it differs from, or is not defined in Forward Sequence, Bidirectional Sequence or Random Access Sequence depending on the traversal characteristics (see Sequence Traversal Concept) of its underlying sequence or sequences.

Expression | Semantics
--- | ---
`UTV(s, f1)` | Creates a unary `transform_view` given sequence, `s` and unary function object or function pointer, `f1`.
`BTV(s1, s2, f2)` | Creates a binary `transform_view` given sequences, `s1` and `s2` and binary function object or function pointer, `f2`.
`TV(tv)` | Copy constructs a `transform_view` from another `transform_view`, `tv`.
`tv = tv2` | Assigns to a `transform_view`, `tv`, from another `transform_view`, `tv2`.

##### Example

    struct square
    {
        template<typename Sig>
        struct result;

        template<typename U>
        struct result<square(U)>
        : remove_reference<U>
        {};

        template <typename T>
        T operator()(T x) const
        {
            return x * x;
        }
    };

    typedef vector<int, short, double> vector_type;
    vector_type vec(2, 5, 3.3);

    transform_view<vector_type, square> transform(vec, square());
    std::cout << transform << std::endl;