if ( opArg2 == opArg )
return super.transform(funcOp, args, opArg) ;
if ( funcOp instanceof E_Exists )
return new E_Exists(opArg2) ;
if ( funcOp instanceof E_NotExists )
return new E_NotExists(opArg2) ;
throw new ARQInternalErrorException("Unrecognized ExprFunctionOp: \n"+funcOp) ;
}