isRoot -- check whether a weight is a root or whether a root is in a parabolic sub root system

Ways to use isRoot:

• isRoot(RootSystem,Parabolic,Root) -- check whether a root is in the sub root system of the parabolic
• isRoot(RootSystem,Weight) -- check whether a weight is a positive root

For the programmer

The object isRoot is a method function.

The source of this document is in WeylGroups.m2:2197:0.