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WeylGroups :: positiveRoots(RootSystem,Parabolic)

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

Synopsis

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