How to set the default argument value of a function.



I know it is possible to define a function with variable number of
arguments by reading the manual here:
http://maxima.sourceforge.net/docs/manual/en/maxima_36.html.

However, I did not find how to define the default values of the arguments
of a function.

For example,

f1(a,[b]):=(a+b[1]+b[2]);

f1(3);

I want b[1] and b[2] to be equal to 1 and 2 by default when they are
omitted when calling f1.

Help would be appreciated.


Leo