[mercury-users] io output exceptions

[Fergus Henderson]

On 14-Nov-2002, Michael Day <mikeday at yeslogic.com> wrote:
> 
> > (1) I/O errors are rare
> > (2) Throwing an exception is usually the right action.
> 
> In that case, why don't input operations throw exceptions?
>
> Ralph says:
> 
> "One expects a result from an input and has to be prepared for at least
> success and eof, so also handling error cases that way seems natural."
> 
> but it does complicate parsing code as you end up with three branches 
> after every operation instead of two.

True, but it's only a minor complication.

Operations that open files don't throw exceptions on I/O errors because
errors when opening files are common, not exceptional.  I don't think
those should change.  For operations which read data from an already-opened
file, we might change the interface in version 2 of the library.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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