On 10 Mar 2008, at 12:37 AM, Donn Cave wrote:
On Mar 9, 2008, at 1:07 PM, Henning Thielemann wrote:
Errors are programming errors and must be fixed as Denis
explained. Thus
there is no need for a complex system of handling these situations at
run-time. The program error might be unexpected but it isn't the
fault of
the user or of the context the program runs in but of the fault of
the
programmer. The program may report "bug detected, send an e-mail
to the
author" but eventually it should quit (at least the buggy thread)
before
worse things happen. This is possible in Haskell but should not be
mixed
up with handling of exceptions like "non-existing file".
I am not sure I see the difference in principle that you see.
An exception is, for me, any state that isn't properly accounted
for in its
immediate context. openFile could return 'Maybe Handle', but it
doesn't,
so the context demands a Handle or an exception.
In the context of this discussion, `Maybe Handle' /is/ an exception
type, because Maybe is an exception monad. As is IO. This
distinction is one between an unusual-but-anticipated code path, and
a case the programmer simply didn't handle at all. The former is an
exception; the latter is an error.
jcc
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