The Radius argument to the AddCircle method requires a Double, but the ActiveX functions make the necessary conversion if you specify a real in AutoLISP. The following table identifies the AutoLISP data type that ActiveX functions will accept in place of the required ActiveX data type. Each row in the table represents a data type used by ActiveX functions. Each column in the table represents an AutoLISP data type. Wherever the intersecting cells contain a plus (+) symbol, you can specify the corresponding AutoLISP data type for the required ActiveX data type.
In some instances an AutoLISP ActiveX function will accept and convert a data type that is not indicated as acceptable by the preceding table, but you should never count on this.