CGAL 4.7 - dD Geometry Kernel: CGAL::Point_d< Kernel > Class Template Reference

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CGAL 4.7 - dD Geometry Kernel

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CGAL::Point_d< Kernel > Class Template Reference
Kernel Objects

`#include <CGAL/Kernel_d/Point_d.h>`

## Definition

An instance of data type `Point_d<Kernel>` is a point of Euclidean space in dimension \( d\).

A point \( p = (p_0,\ldots,p_{ d - 1 })\) in \( d\)-dimensional space can be represented by homogeneous coordinates \( (h_0,h_1,\ldots,h_d)\) of number type `RT` such that \( p_i = h_i/h_d\), which is of type `FT`. The homogenizing coordinate \( h_d\) is positive.

We call \( p_i\), \( 0 \leq i < d\) the \( i\)-th Cartesian coordinate and \( h_i\), \( 0 \le i \le d\), the \( i\)-th homogeneous coordinate. We call \( d\) the dimension of the point.

Downward compatibility

We provide operations of the lower dimensional interface `x()`, `y()`, `z()`, `hx()`, `hy()`, `hz()`, `hw()`.

Implementation

Points are implemented by arrays of `RT` items. All operations like creation, initialization, tests, point - vector arithmetic, input and output on a point \( p\) take time \( O(p.dimension())\). `dimension()`, coordinate access and conversions take constant time. The space requirement for points is \( O(p.dimension())\).

## Types

typedef unspecified_type | LA
| the linear algebra layer.
typedef unspecified_type | Cartesian_const_iterator
| a read-only iterator for the Cartesian coordinates.
typedef unspecified_type | Homogeneous_const_iterator
| a read-only iterator for the homogeneous coordinates.

## Creation

| Point_d ()
| introduces a variable `p` of type `Point_d<Kernel>`.
| Point_d (int d, Origin)
| introduces a variable `p` of type `Point_d<Kernel>` in \( d\)-dimensional space, initialized to the origin.
template<class InputIterator >
| Point_d (int d, InputIterator first, InputIterator last)
| introduces a variable `p` of type `Point_d<Kernel>` in dimension `d`. More...
template<class InputIterator >
| Point_d (int d, InputIterator first, InputIterator last, RT D)
| introduces a variable `p` of type `Point_d<Kernel>` in dimension `d` initialized to the point with homogeneous coordinates as defined by `H = set [first,last)` and `D`: \( (\pm H[0], \pm H[1], \ldots, \pm H[d-1], \pm D)\). More...
| Point_d (RT x, RT y, RT w=1)
| introduces a variable `p` of type `Point_d<Kernel>` in \( 2\)-dimensional space. More...
| Point_d (RT x, RT y, RT z, RT w)
| introduces a variable `p` of type `Point_d<Kernel>` in \( 3\)-dimensional space. More...

## Operations

int | dimension ()
| returns the dimension of `p`.
FT | cartesian (int i)
| returns the \( i\)-th Cartesian coordinate of `p`. More...
FT | operator[] (int i)
| returns the \( i\)-th Cartesian coordinate of `p`. More...
RT | homogeneous (int i)
| returns the \( i\)-th homogeneous coordinate of `p`. More...
Cartesian_const_iterator | cartesian_begin ()
| returns an iterator pointing to the zeroth Cartesian coordinate \( p_0\) of `p`.
Cartesian_const_iterator | cartesian_end ()
| returns an iterator pointing beyond the last Cartesian coordinate of `p`.
Homogeneous_const_iterator | homogeneous_begin ()
| returns an iterator pointing to the zeroth homogeneous coordinate \( h_0\) of `p`.
Homogeneous_const_iterator | homogeneous_end ()
| returns an iterator pointing beyond the last homogeneous coordinate of `p`.
Point_d< Kernel > | transform (const Aff_transformation_d< Kernel > &t)
| returns \( t(p)\).

## Arithmetic Operators, Tests and IO

Vector_d< Kernel > | operator- (const Origin &o)
| returns the vector \( p-O\).
Vector_d< Kernel > | operator- (const Point_d< Kernel > &q)
| returns \( p - q\). More...
Point_d< Kernel > | operator+ (const Vector_d< Kernel > &v)
| returns \( p + v\). More...
Point_d< Kernel > | operator- (const Vector_d< Kernel > &v)
| returns \( p - v\). More...
Point_d< Kernel > & | operator+= (const Vector_d< Kernel > &v)
| adds `v` to `p`. More...
Point_d< Kernel > & | operator-= (const Vector_d< Kernel > &v)
| subtracts `v` from `p`. More...
bool | operator== (const Origin &)
| returns true if `p` is the origin.

## Constructor & Destructor Documentation

template<typename Kernel >
template<class InputIterator >

CGAL::Point_d< Kernel >::Point_d | ( | int | d,
|  | InputIterator | first,
|  | InputIterator | last
| ) |  |

introduces a variable `p` of type `Point_d<Kernel>` in dimension `d`.

If `size [first,last) == d` this creates a point with Cartesian coordinates `set [first,last)`. If `size [first,last) == d+1` the range specifies the homogeneous coordinates \( H = set [first,last) = (\pm h_0, \pm h_1, \ldots, \pm h_d)\) where the sign chosen is the sign of \( h_d\).

Precondition
  `d` is nonnegative, `[first,last)` has `d` or `d+1` elements where the last has to be non-zero.

Requires:
  The value type of `InputIterator` is `RT`.

template<typename Kernel >
template<class InputIterator >

CGAL::Point_d< Kernel >::Point_d | ( | int | d,
|  | InputIterator | first,
|  | InputIterator | last,
|  | RT | D
| ) |  |

introduces a variable `p` of type `Point_d<Kernel>` in dimension `d` initialized to the point with homogeneous coordinates as defined by `H = set [first,last)` and `D`: \( (\pm H[0], \pm H[1], \ldots, \pm H[d-1], \pm D)\).

The sign chosen is the sign of \( D\).

Precondition
  `D` is non-zero, the iterator range defines a \( d\)-tuple of `RT`.

Requires:
  The value type of `InputIterator` is `RT`.

template<typename Kernel >

CGAL::Point_d< Kernel >::Point_d | ( | RT | x,
|  | RT | y,
|  | RT | w = `1`
| ) |  |

introduces a variable `p` of type `Point_d<Kernel>` in \( 2\)-dimensional space.

Precondition
  \( w \neq0\).

template<typename Kernel >

CGAL::Point_d< Kernel >::Point_d | ( | RT | x,
|  | RT | y,
|  | RT | z,
|  | RT | w
| ) |  |

introduces a variable `p` of type `Point_d<Kernel>` in \( 3\)-dimensional space.

Precondition
  \( w \neq0\).

## Member Function Documentation

template<typename Kernel >

FT CGAL::Point_d< Kernel >::cartesian | ( | int | i) |  |

returns the \( i\)-th Cartesian coordinate of `p`.

Precondition
  \( 0 \leq i < d\).

template<typename Kernel >

RT CGAL::Point_d< Kernel >::homogeneous | ( | int | i) |  |

returns the \( i\)-th homogeneous coordinate of `p`.

Precondition
  \( 0 \leq i \leq d\).

template<typename Kernel >

Point_d<Kernel> CGAL::Point_d< Kernel >::operator+ | ( | const Vector_d< Kernel > & | v) |  |

returns \( p + v\).

Precondition
  `p.dimension() == v.dimension()`.

template<typename Kernel >

Point_d<Kernel>& CGAL::Point_d< Kernel >::operator+= | ( | const Vector_d< Kernel > & | v) |  |

adds `v` to `p`.

Precondition
  `p.dimension() == v.dimension()`.

template<typename Kernel >

Vector_d<Kernel> CGAL::Point_d< Kernel >::operator- | ( | const Point_d< Kernel > & | q) |  |

returns \( p - q\).

Precondition
  `p.dimension() == q.dimension()`.

template<typename Kernel >

Point_d<Kernel> CGAL::Point_d< Kernel >::operator- | ( | const Vector_d< Kernel > & | v) |  |

returns \( p - v\).

Precondition
  `p.dimension() == v.dimension()`.

template<typename Kernel >

Point_d<Kernel>& CGAL::Point_d< Kernel >::operator-= | ( | const Vector_d< Kernel > & | v) |  |

subtracts `v` from `p`.

Precondition
  `p.dimension() == v.dimension()`.

template<typename Kernel >

FT CGAL::Point_d< Kernel >::operator[] | ( | int | i) |  |

returns the \( i\)-th Cartesian coordinate of `p`.

Precondition
  \( 0 \leq i < d\).