Thanks all. it's Barcap in NYC.
Hai
On Thu, May 27, 2010 at 11:48 PM, Bill Broadley <b...@broadley.org> wrote:
> On 05/27/2010 08:35 PM, Chanoch (Ken) Bloom wrote:
>> On Thu, 2010-05-27 at 22:08 -0400, Hai Yi wrote:
>>> hi there:
>>>
>>> can anyone look at these two small c++ snippets to see what's wrong
>>> with them? I was interviewed with them...
>
> Out of curiosity, where? (feel free to not answer)
>
>>> 1.
>>> A* createA(){ return new A();}
>>> void fun(){createA();}
>>> What's wrong with the above code?
>>
>> It leaks memory.
>
> Is A defined? Is it that A is allocated but the return value isn't
> checked (for an allocation failure)? Or that the pointer isn't used? Or
> that it leaks?
>
>>> 2.
>>> for(iter=map.begin();iter!=map.end();iter++){
>>> erase(iter++);
>>> iter++;
>>> }
>>> anything wrong with the above code? What's happened for "iter++" internally?
>>
>> 1. erase() is a member function of the map class. It is not a free
>> function. A free function named erase() wouldn't know what
>> container to erase the iterator from.
>> 2. The code only works if map.size() is a multiple of 3. If it
>> isn't, then one of the iter++ operations may try to put iter 2
>> or 3 past the end of the map. If you did this on a raw array, or
>> a vector (whose iterators are usually just pointers to the
>> elements, unless you're in some kind of debug mode),
>> * then the standard doesn't guarantee that you can form
>> the address of the element 2 or 3 past the end of the
>> array,
>> * if you could form that address it would certainly no
>> longer be equal to array.end(), so you'd miss the
>> termination condition.
>
> While true, wouldn't it be simpler to just say that iter is incremented
> 3 times per loop and it's likely that the intent is once? While legal
> in C/C++, in general you shouldn't much with an iteration variable.
> Either turn it into a while (without increment) and handle it in the
> body, or increment in the for loop and don't muck with it in the body.
> _______________________________________________
> vox-tech mailing list
> vox-tech@lists.lugod.org
> http://lists.lugod.org/mailman/listinfo/vox-tech
>
_______________________________________________
vox-tech mailing list
vox-tech@lists.lugod.org
http://lists.lugod.org/mailman/listinfo/vox-tech
