On 06/03/11 21:39, Anders Logg wrote:
> On Sun, Mar 06, 2011 at 10:29:10PM +0100, Marie E. Rognes wrote:
>> On 03/06/2011 10:22 PM, Anders Logg wrote:
>>> On Sun, Mar 06, 2011 at 09:08:10PM +0000, Garth N. Wells wrote:
>>>>
>>>>
>>>> On 06/03/11 21:02, Marie E. Rognes wrote:
>>>>> On 03/06/2011 09:30 PM, nore...@launchpad.net wrote:
>>>>>> if (parameters["max_dimension"].change_count()> 0
>>>>>> && V.dim()> max_dimension)
>>>>>> + {
>>>>>> return true;
>>>>>> -
>>>>>> - // Otherwise, not done.
>>>>>> - return false;
>>>>>> + }
>>>>>> + else
>>>>>> + return false;
>>>>>> }
>>>>>
>>>>>
>>>>> I notice that my early returns keep getting moved into else clauses... I
>>>>> find this approach less readable, especially when there are nested ifs.
>>>>> Why is it the preferred way?
>>>>>
>>>>
>>>> Because your comment basically says else, so I'd say it's better to have
>>>> the code say it consistently.
>>>>
>>>> I find it easier to follow, because it's clear that the function exits
>>> >from the conditional block. The return value is either true or false
>>>> depending on the one true/false evaluation.
>>
>>
>> The code is an if -- else if -- else. I don't see how moving that
>> into an if, if -- else increases consistency.
>>
>>
>>>
>>> I'm not sure we're talking about the same thing here, but I think the
>>> following examples are *good* practice:
>>>
>>> 1. Early return to get rid of special cases
>>>
>>> void foo()
>>> {
>>> // Get rid of some case
>>> if (...)
>>> return;
>>>
>>> // Get rid of another case
>>> if (...)
>>> return;
>>>
>>> // Do main bulk of work here
>>> ...
>>> }
>>>
>>> Alternative using if/else will force main code in one indentation
>>> level.
>>>
>>> 2. Fallback return at end of block
>>>
>>> bool foo()
>>> {
>>> // Handle case 1
>>> if (...)
>>> {
>>> ...
>>>
>>> return true;
>>> }
>>>
>>> // Handle case 2
>>> if (...)
>>> {
>>> ...
>>>
>>> return true;
>>> }
>>>
>>> // No foos found
>>> return false;
>>> }
>>
>>
>> Yep, I prefer 2. to an if -- else if (-- else if) -- else.
>
> It's also logical since the 'else' has no effect. So the policy can be
> to remove code that has zero effect.
>
If it's a straight if - else, I have a pretty strong view that 'else'
should be used. C/C++ don't provide 'else' for nothing.
Related, one strict school of thought says that both 1. and 2. are bad
since a function should only have one exit. We have had memory leaks
because of premature exits.
Garth
> --
> Anders
>
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