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# Real Segments ( real_segment )

Definition

An instance s of the data type real_segment is a directed straight line segment in the two-dimensional plane, i.e., a straight line segment [p, q] connecting two points p, q R2 . p is called the source or start point and q is called the target or end point of s . The length of s is the Euclidean distance between p and q . If p = q , s is called empty. We use line(s) to denote a straight line containing s .

#include < LEDA/geo/real_segment.h >

Types

 real_segment::coord_type the coordinate type (real). real_segment::point_type the point type (real_point).

Creation

 real_segment s(const real_point& p, const real_point& q) introduces a variable s of type real_segment. s is initialized to the segment [p, q] . real_segment s(const real_point& p, const real_vector& v) introduces a variable s of type real_segment. s is initialized to the segment [p, p + v] . Precondition v.dim() = 2 . real_segment s(real x1, real y1, real x2, real y2) introduces a variable s of type real_segment. s is initialized to the segment [(x1, y1),(x2, y2)] . real_segment s introduces a variable s of type real_segment. s is initialized to the empty segment. real_segment s(const segment& s1, int prec = 0) introduces a variable s of type real_segment initialized to the segment s1 . (The second argument is for compatibility with rat_segment.) real_segment s(const rat_segment& s1) introduces a variable s of type real_segment initialized to the segment s1 .

Operations

 real_point s.start() returns the source point of segment s. real_point s.end() returns the target point of segment s. real s.xcoord1() returns the x-coordinate of s.source(). real s.xcoord2() returns the x-coordinate of s.target(). real s.ycoord1() returns the y-coordinate of s.source(). real s.ycoord2() returns the y-coordinate of s.target(). real s.dx() returns the xcoord2 - xcoord1 . real s.dy() returns the ycoord2 - ycoord1 . real s.slope() returns the slope of s . Precondition s is not vertical. real s.sqr_length() returns the square of the length of s. real s.length() returns the length of s. real_vector s.to_vector() returns the vector s.target() - s.source(). bool s.is_trivial() returns true if s is trivial. bool s.is_vertical() returns true iff s is vertical. bool s.is_horizontal() returns true iff s is horizontal. int s.orientation(const real_point& p) computes orientation( s.source() , s.target() , p ) (see below). real s.x_proj(real y) returns p .xcoord(), where p line(s) with p .ycoord() = y . Precondition s is not horizontal. real s.y_proj(real x) returns p .ycoord(), where p line(s) with p .xcoord() = x . Precondition s is not vertical. real s.y_abs() returns the y-abscissa of line(s) , i.e., s.y_proj(0). Precondition s is not vertical. bool s.contains(const real_point& p) decides whether s contains p . bool s.intersection(const real_segment& t) decides whether s and t intersect in one point. bool s.intersection(const real_segment& t, real_point& p) if s and t intersect in a single point this point is assigned to p and the result is true, otherwise the result is false. bool s.intersection_of_lines(const real_segment& t, real_point& p) if line(s) and line(t) intersect in a single point this point is assigned to p and the result is true, otherwise the result is false. real_segment s.translate(real dx, real dy) returns s translated by vector (dx, dy) . real_segment s.translate(const real_vector& v) returns s + v , i.e., s translated by vector v . Precondition v .dim() = 2. real_segment s + const real_vector& v returns s translated by vector v . real_segment s - const real_vector& v returns s translated by vector - v . real_segment s.perpendicular(const real_point& p) returns the segment perpendicular to s with source p and target on line(s) . real s.distance(const real_point& p) returns the Euclidean distance between p and s . real s.sqr_dist(const real_point& p) returns the squared Euclidean distance between p and s . real s.distance() returns the Euclidean distance between (0, 0) and s . real_segment s.rotate90(const real_point& q, int i=1) returns s rotated about q by an angle of i x 90 degrees. If i > 0 the rotation is counter-clockwise otherwise it is clockwise. real_segment s.rotate90(int i=1) returns s .rotate90(s .source(),i). real_segment s.reflect(const real_point& p, const real_point& q) returns s reflected across the straight line passing through p and q . real_segment s.reflect(const real_point& p) returns s reflected across point p . real_segment s.reverse() returns s reversed.

Non-Member Functions

 int orientation(const real_segment& s, const real_point& p) computes orientation( s.source() , s.target() , p ). int cmp_slopes(const real_segment& s1, const real_segment& s2) returns compare(slope(s1 ), slope(s2 )). int cmp_segments_at_xcoord(const real_segment& s1, const real_segment& s2, const real_point& p) compares points l1 v and l2 v where li is the line underlying segment si and v is the vertical straight line passing through point p . bool parallel(const real_segment& s1, const real_segment& s2) returns true if s1 and s2 are parallel and false otherwise.

Next: Real Rays ( real_ray Up: Basic Data Types for Previous: Real Points ( real_point   Contents   Index
Christian Uhrig 2017-04-07