Why exceptions for error handling is so important

[Dmitry Olshansky via Digitalmars-d]

13-Jan-2015 02:01, "Ola Fosheim =?UTF-8?B?R3LDuHN0YWQi?= 
<ola.fosheim.grostad+dlang at gmail.com>" пишет:
> On Monday, 12 January 2015 at 22:06:32 UTC, deadalnix wrote:
>> If you put aside performance concerns, exceptions for control flow
>> also tend to make many code path implicit and makes for very
>> unreadable/unmaintainable code.
>
> But exceptions are control flow. There is no such thing as normalized
> control flow, all state changes implies "control flow". Think in terms
> of a state machine. You could just remove all variables and only have a
> big state machine (assuming finite dimensions). Every single state
> transition implies flow of control.
>
> The control flow you see in the source code is just the programmer's
> "rendition" of control flow. Exceptions is a mechanism for getting
> cluttering resolution out of that rendition to make the code more
> readable and maintainable. The goal is to retain the meat of the
> computation and remove the noise.
>
> Or to put it differently, there are many ways to write the same
> function. Good use of exceptions removes the clutter and leaves the
> things you care about visible. It's a mechanism, not a moral issue or a
> religion.
>
> So there is nothing wrong with throwing HTTPStatus(409) or
> HTTPStatus(201), even though it returns state to the environment. If
> that means the code is more maintainable and more likely to be correct,
> then that is good use of the mechanism.

Actually I agree  - exceptions are mechanism. Stressing _exceptional_ as 
in "happening very rarely" is just a poor excuse to never optimize this 
control-flow mechanism. I guess C/C++ inspired languages would never 
have fast exceptions simply because of the mindset with the perception 
of them being non-important or rare. Big adopters of C++ often avoided 
exceptions entirely to not pollute binaries with EH-code only making 
this issue worse.

In contrast, Java optimizes exceptions and re-writes many try/catch to 
plain "gotos on error" control flows.

-- 
Dmitry Olshansky