isRoot(RootSystem,Weight) -- check whether a weight is a positive root

Synopsis

• Function: isRoot

• Usage:

  isRoot(R,p)

• Inputs:
  • R, an instance of the type RootSystem
  • p, an instance of the type Weight
• Outputs:
  • a Boolean value, true if p is a root in R and false otherwise

Description

i1 : R=rootSystemE(6)

o1 = RootSystem{...8...}

o1 : RootSystem

i2 : p=simpleRoot(R,1)

o2 = |  2 |
     |  0 |
     | -1 |
     |  0 |
     |  0 |
     |  0 |

o2 : Root

i3 : isPositiveRoot(R,-p)

o3 = false

i4 : isRoot(R,-p)

o4 = true