Boost C++ Libraries - transform

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;