SQL Function Parameter default as select

Question

Function A, scalar, returns smallint (a year)
Function B, scalar, returns smallint (a month)
Function C, table, displays users based on year and month.

They work fine.

I would like to set default parameter of Function C to come from Func A & B like:

@year smallint = SELECT FunctA(), @month smallint = SELECT FunctB()

Is there anyway around this?

We are on Azure SQL Managed Instance.

Answer 1

On thing you could use is something like

IF @year IS NULL
BEGIN
  SET @year = functa();
END;

IF @month IS NULL
BEGIN
  SET @month = functb();
END;

(or whatever the analog syntax is in the DBMS you didn't disclose).
And when you want the defaults, pass NULLs as parameters.