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List:       kde-commits
Subject:    Re: KDE/kdelibs/kdecore
From:       Simon Hausmann <hausmann () kde ! org>
Date:       2007-01-14 14:38:24
Message-ID: 200701141538.32666.hausmann () kde ! org
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On Sunday 14 January 2007 15:07, Thiago Macieira wrote:
> Albert Astals Cid wrote:
> >Add const & to foreach variables so you use the value that is in the
> > container instead of creating a temporal variable and using the copy
> > constructor
>
> Instead, remove the foreach and use iterators.
>
> That improves code performance.
>
> 	foreach (const Type &varname, list)
> becomes:
> 	QList<Type>::ConstIterator it = list.constBegin();
> 	QList<Type>::ConstIterator end = list.constEnd();
> 	for ( ; it != end; ++it) {
> 		const Type &varname = *it;

I don't think it is worth the uglification. foreach is too beautiful for 
that :)

If you compare the code to which foreach() expands with gcc to a manually 
written loop like above you'll notice that the only difference potentially 
affecting performance is that foreach() creates a copy of the implicitly 
shared container. I think the additional atomic refcount is totally 
negligible here.

Simon

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