GAP Manual: 13.6. IsCycInt

IsCycInt( obj )

returns true if obj is a cyclotomic integer (see Cyclotomic Integers), false otherwise. Will signal an error if obj is an unbound variable.

    gap> IsCycInt( 0 ); IsCycInt( E(3) ); IsCycInt( 1/2 * E(3) );
    true
    true
    false

IsCycInt is an internal function.