This package provides classes for constructing four kinds of cone-based spanners (Yao graph, Theta graph, Half Yao graph and Half Theta graph) given a set of vertices on the plane. Both exact and inexact constructions are implemented. In exact construction, the cone boundaries are calculated using roots of polynomials (requiring `CORE::Expr` or `LEDA::real`). In inexact construction, the cone boundaries are calculated using an approximate Pi (3.14159265358979323846), which is still accurate enough for most applications. Moreover, for visualization purpose, this package provides functions to generate the data and script files used by Gnuplot to plot the constructed graphs.
