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From Andre Fischer <awf....@gmail.com>
Subject Re: Improvements of OUString
Date Wed, 04 Dec 2013 10:42:16 GMT
On 04.12.2013 11:12, Herbert Duerr wrote:
> On 04.12.2013 07:20, Andrew Douglas Pitonyak wrote:
>> As Herbert said, this directly expresses what it checks. I would add
>> "and it reads better".
>>
>> There are other reasons, however; for example, depending on the
>> implementation, it may be significantly faster than comparing against
>> the length. For one implementation it may not matter, but, if you change
>> the implementation in the future, it may.
>
> Yes. Especially considering that the "length of a string" is somewhat 
> ambiguous. Currently getLength() returns the number of codepoints in 
> the strings encoding (e.g. UTF-16).
>
> But one could also reasonably define the length of a string as the 
> number of unicode codepoints. This number is different from 
> getLength() if unicode surrogates were involved or unicode normal 
> forms were taken into consideration.
>
>> Uniformity is another possible reason (assuming other classes also
>> implement isEmpty()). If you become used to using the expressive form
>> (ie, using isEmpty() rather than comparing size), then you can leave
>> optimizing the call to the class implementer rather than worrying about
>> the correct way to do it.
>
> For historic reasons the STL and TR1 containers use "empty()" to check 
> for emptiness and clear() to empty the container.
>
> In the previous sentence I intentionally used "empty" once as an 
> adjective and once as a verb to show that the method name "empty()" is 
> ambiguous. Therefore I preferred to use the Java inspired method name 
> "isEmpty()" for checking the emptiness of a string.
>
>> I have seen empty strings checked by comparing
>> the length to zero, and even using a string compare against an empty
>> string.
>
> Indeed: In our current codebase there are all kinds of variants for 
> this simple check. E.g.
>     aString == OUString()
>     aString.equalsAscii("")
>     aString.equals( OUString())
>     aString.compareTo( OUString(""))
>     aString.compareToAscii( "")
>     aString.getLength() == 0
>     aString.getLength() < 1
> and the related checks:
>     aString.getLength() > 0
>     aString.getLength() >= 1
> Also there was the now already eliminated buggy variant
>     if( aString)
>
> With the new method all these could be cleanly consolidated.
>
> I must admit that the long discussion thread over the seemingly simple 
> new method "isEmpty()" is somewhat scary to me...

Seemingly is the operative word.
Personally, I find "aString.getLength() < 1" much more scary.

Do you want to extend the documentation of OUString with some of what we 
found out in this thread (getLength(), isEmpty(), etc) or do you want 
somebody else to do it?

-Andre

>
> Herbert
>
>
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