Qt-interest Archive, February 2007
Basic QStringList sort question
Message 1 in thread
Thank you for reading this.
I need to sort the members of a QStringList in QString length order (longest
words first). The documentation mentions using QMap <int> <QString> for
nonstandard sorts but I can't see how this is done. Can someone point me in
the right direction?
I started to code a bubble sort method but I'd like to see how Qt handles
unusual sorts.
Regards,
Phil.
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Message 2 in thread
On 2/18/07, Phil <phillor@xxxxxxxxxxx> wrote:
> Thank you for reading this.
>
> I need to sort the members of a QStringList in QString length order (longest
> words first). The documentation mentions using QMap <int> <QString> for
> nonstandard sorts but I can't see how this is done. Can someone point me in
> the right direction?
>
> I started to code a bubble sort method but I'd like to see how Qt handles
> unusual sorts.
One of the "sort" algorithm overloads from standart C++ library,
accepts custom comparation functor:
http://www.sgi.com/tech/stl/sort.html
The code using it would look something like this (don't take it
literraly - I didn't compile it):
template<typename T>
struct LengthComp
{
bool operator()(const T& first,const T& second) {
return first.length() < seond.length();
}
};
QStringList list;
//...
std::sort(list.begin(), list.end(), LengthComp<QString>());
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Message 3 in thread
On 2/18/07, Pavel Antokolsky aka Zigmar <zigmar@xxxxxxxxx> wrote:
> On 2/18/07, Phil <phillor@xxxxxxxxxxx> wrote:
> > Thank you for reading this.
> >
> > I need to sort the members of a QStringList in QString length order (longest
> > words first). The documentation mentions using QMap <int> <QString> for
> > nonstandard sorts but I can't see how this is done. Can someone point me in
> > the right direction?
> >
> > I started to code a bubble sort method but I'd like to see how Qt handles
> > unusual sorts.
>
> One of the "sort" algorithm overloads from standart C++ library,
> accepts custom comparation functor:
> http://www.sgi.com/tech/stl/sort.html
And there is also qSort(), available if you have access to stl.
http://doc.trolltech.com/4.2/qtalgorithms.html#qSort
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Message 4 in thread
On 2/18/07, Robin Ericsson <lobbin@xxxxxxxxx> wrote:
> On 2/18/07, Pavel Antokolsky aka Zigmar <zigmar@xxxxxxxxx> wrote:
> > On 2/18/07, Phil <phillor@xxxxxxxxxxx> wrote:
> > > I need to sort the members of a QStringList in QString length order (longest
> > > words first). The documentation mentions using QMap <int> <QString> for
> > > nonstandard sorts but I can't see how this is done. Can someone point me in
> > > the right direction?
> > One of the "sort" algorithm overloads from standart C++ library,
> > accepts custom comparation functor:
> > http://www.sgi.com/tech/stl/sort.html
> And there is also qSort(), available if you have access to stl.
> http://doc.trolltech.com/4.2/qtalgorithms.html#qSort
The qSort uses type's built-in comparison (operator<()), and does not
allows to specify custom comparator, as the STL algorithm I've
mentioned. If qSort will be called on QStringList, they will be sorted
alphanumerically and not by length, as Phil wants.
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Message 5 in thread
Hi,
Pavel Antokolsky aka Zigmar wrote:
>> And there is also qSort(), available if you have access to stl.
>> http://doc.trolltech.com/4.2/qtalgorithms.html#qSort
> The qSort uses type's built-in comparison (operator<()), and does not
> allows to specify custom comparator, as the STL algorithm I've
> mentioned. If qSort will be called on QStringList, they will be sorted
> alphanumerically and not by length, as Phil wants.
There is more that one version of qSort: one takes just a container
reference, one takes start & end iterators and finally one takes start &
end iterators and a compare function/function object.
Tim
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Message 6 in thread
On 2/18/07, Tim Dewhirst <tim@xxxxxxxxxxxxx> wrote:
> There is more that one version of qSort: one takes just a container
> reference, one takes start & end iterators and finally one takes start &
> end iterators and a compare function/function object.
Oh, ok. You are right. Sorry. Missed this.
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Message 7 in thread
----- Original Message -----
From: "Pavel Antokolsky aka Zigmar" <zigmar@xxxxxxxxx>
To: <qt-interest@xxxxxxxxxxxxx>
Sent: Sunday, February 18, 2007 6:23 PM
Subject: Re: Basic QStringList sort question
> The code using it would look something like this (don't take it
> literraly - I didn't compile it):
>
> template<typename T>
> struct LengthComp
> {
> bool operator()(const T& first,const T& second) {
> return first.length() < seond.length();
> } };
>
> QStringList list;
> //...
>
> std::sort(list.begin(), list.end(), LengthComp<QString>());
>
Thanks Zigmar and everyone who replied.
I wasnât able to manipulate this piece of code to get it to compile without
errors but it is along the lines of what I had in mind.
Although, no doubt, not as elegant as Zigmarâs solution I did continue with
my efforts to code a bubble sort method which does work.
Regards,
Phil.
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Message 8 in thread
Phil wrote:
> Thank you for reading this.
>
> I need to sort the members of a QStringList in QString length order
> (longest words first). The documentation mentions using QMap <int>
> <QString> for nonstandard sorts but I can't see how this is done. Can
> someone point me in the right direction?
>
> I started to code a bubble sort method but I'd like to see how Qt handles
> unusual sorts.
No need to create your own bubble sort.
http://doc.trolltech.com/4.2/qtalgorithms.html#qSort-2 should be what you
need. Just supply a function that compares the lengths of the strings.
HTH,
André
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