GAP:IsCharacteristicInParent

Function type
IsCharacteristicInParent is a GAP function that takes as input an argument representing a group, and outputs a Boolean answer (true/false).

Behavior
The function is rare in that it depends not just on the isomorphism class of the group provided but the context in which the group was defined. Specifically, it invokes GAP's Parent attribute/function to determine the parent group in which the given group resides, and then determines whether the given group is characteristic in its parent.

To interpret this function, it may be useful to first determine whether the input group equals its own parent. This can be done by the Parent function:

G = Parent(G);

Package requirements
This function requires the Sonata package. If the package is present but not loaded, it can be loaded by the command:

LoadPackage("sonata");

Related functions

 * Parent: Outputs the parent group for a given group
 * IsNormal
 * IsCharacteristic