Error with callable

From: Linux Man (steven_82m_at_hotmail.com)
Date: 03/23/04 

Date: 23 Mar 2004 10:36:36 -0800

I got the following error. Would you please let me know what it means?

ERROR: Type error: `callable' expected, found `"digits('10101010')."'
   Exception: (15) process(10, "101010", 4) ?

I wanted to assert "digits('10101010')." and to see whether it returns the dear

"Yes"!!. I did this by typing "assert(X)" in one of the procedures which is

called by another procedure.

Thanks