OpenROAD lets you pass simple variables to a 3GL procedure. You can also pass objects and arrays as described in the Language Reference Guide online help and in Using 3GL in Your Application (see Using 3GL in Your Application). When you pass values to a 3GL procedure, the data type of the values must match the data types of the parameters receiving them in the procedure.

The following table lists the 4GL simple data types and describes their corresponding 3GL data type declarations:

You can use the byref option with any variable that you pass to a 3GL procedure, regardless of the variable's data type.

You cannot pass a char or varchar variable that contains an embedded zero byte (hexadecimal'00') to a 3GL procedure. No runtime error occurs, but a truncated version of the 4GL variable may be passed.

When a 4GL date variable passes to a 3GL procedure by name, or when the return type of a 3GL procedure is date, 4GL receives it back from the 3GL procedure as a 25-byte string and must then convert it to the internal date format. The date must be valid before the conversion can succeed.

Passing a 4GL variable containing a null value to a 3GL procedure causes a runtime error. Use the ifnull function and is null comparison operator to pass nullable types between 3GL and 4GL, for example:

This reference returns the value of v1 if v1 is not null; otherwise, if v1 is null, it returns the value of v2. The variables v1 and v2 must be the same data type.

If an impossible value exists for the argument, use the impossible value to indicate a null:

If no impossible value exists for the argument, pass a separate indicator variable to indicate a null argument: