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4.25 fan
In order to use convex objects in Singular, Singular uses gfanlib,
a C++ library for convex geometry by Anders N. Jensen.
Please check the readme file for installation instructions.
The library gfan_lib provides this C++ library and an interface to it.
Some functions require polymake : polymake_lib provides
an interface to it.
A polyhedral fan is a collection of cones closed under taking intersections and
faces.
| fan f; // ambient dim 0, no cones, lineality
// space = ambient space
fan f = emptyFan(int n); // ambient dim = n, no cones,
// symmetry subgroup = <e>
fan f = n; // synonymous convenience method for
// 'fan f = emptyFan(n)'
fan f = emptyFan(
optional intmat G); // symmetry group generated by rows of
// G; ambient dim = number of columns
// of G
// Here a row r = r_1, ...r_n represents the permutation
// which takes i to r_i. SINGULAR will check for the validity
// of the provided rows, i.e. whether {r_1,...,r_n} = {1,...,n}
fan f = fullFan(int n); // ambient dim = n, the fan consists of
// one cone which equals the ambient
// space, symmetry subgroup = <e>
fan f = fullFan(
optional intmat G); // symmetry group generated by rows of
// G; ambient dim = number of columns
// of G; the fan consists of one cone
// which equals the ambient space
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See also gfan_lib.
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