Re: A Modest Proposal

["R. Jeff Porter" <rjporter@lbl.gov>]

I agree also.
Since the QO is the primary contact for the user code, it
seems that this is where the modifications should go ...
e.g. the QO should catch the QE's exceptions but return
values rather than throw exceptions.  This is true now for
PercentComplete but I'll relook at other relevant places.

Jeff


>I vote in favor of Dave's proposal. -- Doug
>
>> -----Original Message-----
>> From: David M. Malon [mailto:malon@anl.gov]
>> Sent: Wednesday, June 10, 1998 9:27 AM
>> To: challenge@sseos.lbl.gov
>> Cc: malon@anl.gov
>> Subject: A Modest Proposal
>>
>>
>> I'm in the middle of tracking down a bug in which the Query
>> Object - Query
>> Estimator duo throw an exception when PercentComplete() is
>> invoked--someone
>> thinks the query state has become invalid before the iterator has
>> received
>> all the data.  That's not what I'm writing about, but it motivates this
>> note.
>>
>> -> I propose that accessor functions like PercentComplete, and
>> even things
>> -> like minNumEvents, should NOT throw exceptions.
>>
>>    They should instead return "innocuous" values, and we should
>> document our
>>    way out of any inconsistencies.  I realize that one could make an
>>    argument for notifying the user that her query doesn't exist, rather
>>    than telling her that it's 0% complete, but if we force a user to wrap
>>    every effort to retrieve an integer from our components in
>> try/catch blocks,
>>    and kill her code whenever anything goes even slightly awry if
>> she fails to
>>    do so, we will win no fans (...and I want people to LIKE us; well, me,
>>    anyway).
>>
>>    Consider the single line
>>
>>  cout<<"iterator returned "<<OOI.numFiles()<<" and
>> "<<OOI.numRefs()<<" refs.";
>>
>>    Do we want to require that the user write:
>>
>> ************************************************
>>
>>    int nFiles = 0;
>>    int nRefs = 0;
>>    cout<<"iterator returned ";
>>    try {
>>     nFiles = OOI.numFiles();
>>    }
>>    catch(...) {
>> //   "Switch" block to set nFiles or terminate cleanly, depending
>> upon the
>> //   particular exception, should go here.
>>    }
>>    cout<<nFiles<<" and ";
>>    try {
>>     nRefs = OOI.numRefs();
>>    }
>>    catch(...) {
>> //   "Switch" block to set nFiles or terminate cleanly, depending
>> upon the
>> //   particular exception, should go here.
>>    }
>>    cout<<nRefs<<" refs.";
>>
>> ************************************************
>>
>>    Imagine doing this every time you want to touch a datum!  No one wants
>>    to code like this, and I don't believe that doing so improves software
>>    quality.
>>
>>    I am happy to propose that users wrap query construction,
>> estimation, and
>>    execution in try/catch blocks, but simple accessors?
>>
>> What do you think?
>>
>> David
>>
>>
>>
>
>