boost::bind annoyance with home grown iterator

[joe]

I'm having an annoyance with a boost::bind failure that I can't figure
out. I'm using an iterator and have all the required fields for
iterator (value_type, etc).

I'm trying to call the function:

find(obj.begin(),
obj.end(),
boost::bind(std::greater<double>(), _1, 4.4);

which gives the error:
stl_algo.h:172: error: no match for 'operator==' in (&_first)-

MyIter<T>:perator* [with T = double]() == __val'

I'm surprised this fails, because all the following work fine:
double a = *obj.begin();
double b = *obj.begin();

and most telling:
bool a = (*obj.begin() == 4.4);

since the code in stl_algo.h is doing exactly that. What could boost
be doing to the _1 placeholder? I assumed it did little more than use
operator* on each iterator as it is passed them.

Any ideas?

 

[joe]

Any ideas?

I need to use find_if of course. that'll teach me to post too early

 

[Kira Yamato]

I'm having an annoyance with a boost::bind failure that I can't figure
out. I'm using an iterator and have all the required fields for
iterator (value_type, etc).

I'm trying to call the function:

find(obj.begin(),
obj.end(),
boost::bind(std::greater<double>(), _1, 4.4);

which gives the error:
stl_algo.h:172: error: no match for 'operator==' in (&_first)-

MyIter<T>:perator* [with T = double]() == __val'

That's because _1 is not of type double, but rather of type

boost::lambda:laceholder1_type.

Have you tried using boost.lambda instead?

using namespace boost::lambda;

find_if(obj.begin(), obj.end(), _1 > 4.4);

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