Question about part of an expression in a DI Studio job

[TurnTheBacon]

I'm working in a DI Studio job that someone else have created, and have a question.

One of the variables in an extract is called Birth_DT. It's mapped in from two variables from the previous work table, namely Birth_DT and Master_ID (which is the PK). It has the following expression:

coalesce(BIRTH_DT, fnr_birthdate(MASTER_ID))

I'm well aware of how coalesce works, but what does "fnr_birthdate(MASTER_ID)" do? The term "fnr_birthdate" doesn't appear anywhere else in the code.

Thanks.

[Patrick]

If this code works then fnr_birthdate() looks to me very much like a user defined function using PROC FCMP Base SAS(R) 9.3 Procedures Guide, Second Edition