positiveRoots(RootSystem,Parabolic) -- the set of all positive roots in a parabolic sugroups

Synopsis

• Function: positiveRoots
• Usage:
positiveRoots(R,P)
• Inputs:
• Outputs:
• a set, of all positive roots of R that are written as sums of roots corresponding to reflexions in P

Description

 i1 : R=rootSystemA(4) o1 = RootSystem{...8...} o1 : RootSystem i2 : P=parabolic(R,set{1,2}) o2 = set {1, 2} o2 : Parabolic i3 : positiveRoots(R,P) o3 = set {| -1 |, | 1 |, | 2 |} | 2 | | 1 | | -1 | | -1 | | -1 | | 0 | | 0 | | 0 | | 0 | o3 : Set