N_PARAMS
 
The 
 
N_PARAMS function returns the number of non-keyword parameters used in calling an IDL procedure or function. This function is only useful within IDL procedures or functions. User-written procedures and functions can use N_PARAMS to determine if they were called with 
 
optional parameters.
NOTE: 
 
In the case of object method procedures and functions, the SELF argument is not counted by N_PARAMS.
 
Calling Sequence
 
Result = N_PARAMS()
 
 
Arguments
 
None. This function always returns the number of parameters that were used in calling the procedure or function from which N_PARAMS is called.