Re: Compile error when use Boost::lambda::bind function

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Sun, 25 Feb 2007 22:31:08 -0500

Message-ID:

<CI6dnURuGIDhyX_YnZ2dnUVZ_qi3nZ2d@comcast.com>

silverburgh.meryl@gmail.com wrote:

I have code which uses Boost lambda in a template like this:
using namespace boost::lambda;

template<class T>
bool lessThanXY( T& src, T& dest ) {

return (src.getY() < dest.getY());
}

template<class T1, class T2>
void sortXY(T1& list) {

sort( list.begin(), list.end(), bind(::lessThanXY<T2>, *(_1),

*(_2) ) );
}

But when I instantiate the template like this, I get the following
compile error:

class Rect;
typedef list<Rect*> RectList;

void sortXYRectList(RectList& rl) {
sortXYWithThreshold<RectList, Rect>(rl);
}

/usr/include/boost/lambda/detail/lambda_traits.hpp:389: error:
ignoring 'const' qualifiers added to function type 'bool ()(Rect&,
Rect&)const'
gmake[5]: *** [RectUtils.o] Error 1

Can you please tell me how to fix my problem ? I did not use 'const'
anywhere in my template, why I get this error:

error: ignoring 'const' qualifiers added to function type 'bool
()(Rect&, Rect&)const'

I don't know the contents (implementation) of 'lambda_traits', but
apparently since you _did not_ use 'const' with the arguments of
your lessThanXY function, it has to drop its own 'const' it probably
applied somewhere on the road to 'lessThanXY'. And why _didn't_ you
use 'const'? Your 'lessThanXY' doesn't attempt to change its args,
does it? So its signature should be "bool (T const&, T const&)".
Try it.

V
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