IsBooleanNearring( nr )  
A right near-ring N is called boolean if all its elements are idempotent with respect to multiplication.
The function IsBooleanNearring simply checks if all elements
are idempotent and returns the according boolean value 
true or false.
gap> IsBooleanNearring( LibraryNearring( "S3", 25 ) ); false
GAP 3.4.4