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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

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;

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