Version 5.0 The LEDA User Manual

double v.zcoord( ) returns the second cartesian coordinate of v.
int compare by angle(const vector& v1 , const vector& v2 )
vector cross product(const vector& v1 , const vector& v2 )
4. Implementation
For a non-zero vector v let α(v) be the angle by
which the positive x-axis has to be turned counterclockwise
until it aligns with v. The function compares
the angles defined by v1 and v2 , respectively.
The zero-vector precedes all non-zero vectors in the
angle-order.
returns the cross product of the three-dimensional
vectors v1 and v2 .
Vectors are implemented by arrays of real numbers. All operations on a vector v take
time O(v.dim()), except for dim and [ ] which take constant time. The space requirement
is O(v.dim()).
Be aware that the operations on vectors and matrices incur rounding errors and hence are
not completely reliable. For example, if M is a matrix, b is a vector, and x is computed
by x = M.solve(b) it is not necessarily true that the test b == M ∗ x evaluates to true.
The types integer vector and integer matrix provide exact linear algebra.