Version 5.0 The LEDA User Manual

15.4 Sets of Parallel Segments ( segment set )
1. Definition
An instance S of the parameterized data type segment set is a collection of items
(seg item). Every item in S contains as key a line segment with a fixed direction α (see
data type segment) and an information from data type I, called the information type of
S. α is called the orientation of S. We use to denote the item with segment s and
information i. For each segment s there is at most one item ∈ S.
#include < LEDA/geo/segment set.h >
2. Creation
segment set S;
creates an empty instance S of type segment set with orientation
zero, i.e., horizontal segments.
segment set S(int rot);
segment set S(double a);
creates an empty instance S of type segment set with orientation
rot · π/2.
creates an empty instance S of type segment set with orientation
a. (Note that there may be incorrect results due to rounding
errors.)
3. Operations
segment S.key(seg item it) returns the segment of item it.
Precondition: it is an item in S.
const I& S.inf(seg item it) returns the information of item it.
Precondition: it is an item in S.
seg item S.insert(const segment& s, const I& i)
seg item S.lookup(const segment& s)
list S.intersection(const segment& q)
associates the information i with segment s. If
there is an item in S then j is replaced
by i, else a new item is added to S. In
both cases the item is returned.
returns the item with segment s (nil if no such
item exists in S).
returns all items ∈ S with s ∩ q ≠ ∅.
Precondition: q is orthogonal to the segments in
S.