Exception Handling in Insight

[Luis Ibanez]

Hi,


I fully agree with the advantages of using
exceptions described in the white paper
sent by Josh.

My only comment is about the implementation
used in VISPack.  The base class for error
(exceptions) has an "enum" type with error codes
and an array of strings (messages) associated
with the error codes.

enum Err_t { Undef_t=0......}
const char ErrType [][ErrType_sz] = {"Undefined","Out of
range".....}

This is a bit contradictory with the statements
presented in the paper, because is still using the
mechanism of setting error codes that have to
be tested elsewhere. It is in some way like keeping
the "errno"  C variable alive but hidding inside
the error class.

Each time that a new error type is added this list
will have to be modified.

It will be cleaner to follow the recomendations
of the paper an implement a hierarchy of classes
in which there is a class corresponding to each
one of the possible error types. The identity of
the class itself will define the type of error produced.

The message can be initialized with a default message
in the constructor of each specific error class.

New error types can be added just by creating new
classes deriving from the ones already existing in
the hierarchy.



Anyway, this is just an implementation detail,
I think it will be for our advantage to use
exceptions as error handling mechanism as Josh
proposed.


-----

Additional information on the use
of exceptions can be found in

Effective C++ CD
Addison-Wesley
Scott Meyers
ISBN 0-201-60614-3

Some advices about how to
make good use of exceptions
can be found in :

C++ Report
http://www.creport.com/
March 1996
"Coping with Exceptions"
by Jack W. Reeves.

and  in C++ Report too
(sep, and nov-dec 1997)
"Exception-Safe Generic Containers"
by Herb Sutter
With comments about how to safely
use exception with templates.

-----




Luis.


--

______________________________________________________________________

Luis Ibanez
Research Assistant Professor - Division of Neurosurgery
University of North Carolina at Chapel Hill
Sitterson Hall, CB#3175, Chapel Hill, NC 27599
email : ibanez at cs.unc.edu       home  :
http://www.cs.unc.edu/~ibanez
phone : (919)-962-1907          fax   : (919)-962-1799

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