About use of specific error
Markus Gaelli
gaelli at emergent.de
Thu Mar 2 12:49:35 UTC 2006
Hi Boris,
>> The consequence is that it can be tedious to capture only specific
>> error.
> Yes, it is often necessary to ask an exception for its message
> text to understand what happened.
Could you give an example please?
I am still not convinced that the idiom of "first (possibly) hitting
the wall, and then asking for the door" is a good one to teach
students programming.
I think it would be better to teach students a _defensive_ way of
programming, that is to ask first, if everything is ok, using some
boolean queries and if these queries do not exist, let them write
these queries and _not_ exception hierarchies.
Exceptions are a way of goto programming and can become quite hairy
to use. I am glad to be in sync here with Andrew Thomas and Dave Hunt
in their nice book about the pragmatic programmer.
They write something like using exceptions should be actually saved
for situations, the developer cannot predict, such as external io-
failures etc.
I am all for letting the programmers know which precondition they
violated calling a method, but only for debugging their code, and not
for using that info _in_ their code.
I am aware that there is a slight performance penalty to ask if
everything is ok first all the times, also when everything _is_ ok.
But I'd teach above idiom more as the exception than as the
rule... ;-) -- if at all.
Cheers,
Markus
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