Vector contains?

Hello, I was just wondering how I would check to see if a vector contains an element. I've been searching but nothing ever comes up when I google vector contains for C++. Was wondering if someone could let me know. Thanks.

http://www.cppreference.com/wiki/stl/algorithm/find

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Mats

hey thnx =)

so i implemented the vectorFind method like so but then i get this error

Code:

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Severity and Description        Path        Resource        Location        Creation Time        Id
/usr/include/c++/4.2/bits/stl_algo.h no match for ‘operator==’ in ‘__first.__gnu_cxx::__normal_iterator<_Iterator, _Container>::operator* [with _Iterator = Dependency*, _Container = std::vector<Dependency, std::allocator<Dependency> >]() == __val’                phase1        line 216        1223652736055        499

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here is a chunk of my code

Code:

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result = find( dependencyList.begin(), dependencyList.end(), d);

            if(result == dependencyList.end()){
                        dependencyList.push_back(d);
                        isTrue = true;
            }
            else
            isTrue = true;

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So your object doesn't have a "operator==" I suppose?

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Mats

just to clarify

i should have #include <algorithm> in

in my header file
and using namespace std;

right?

That's all fine, I guess. result should be a list<type>::iterator.

You should never have using namespace std; in a header file. But the find algorithm is in the std namespace.

>> result should be a list<type>::iterator. <<
You mean std::vector<Dependency>::iterator or std::vector<Dependency>::const_iterator, right?

Also, TaiL, do your items have to be in the vector in a certain order? It might make more sense to use a different container if the order of the items doesn't matter. For example, a set<Dependency> might be more appropriate. It is built to allow you to add items and look them up to see if they exist already. In fact, you can insert an item and it will just fail if it already exists.

The order of dependencies does matter, since apparently he's building a work queue.

Still, I think in this case I'd use an ADT like a linked hash set. Or build a real graph and do a topological sort.

Either way, work queues are problematic for parallelization.

Quote:

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Originally Posted by Daved

>> result should be a list<type>::iterator. <<
You mean std::vector<Dependency>::iterator or std::vector<Dependency>::const_iterator, right?

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yeah thats what i was asking about. Sorry.

Its actually recommended to use a vector =\ so should i be using std::vector<Dependency>:;const_iterator or std::vector<Dependency>iterator??

Quote:

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Originally Posted by Daved

>> result should be a list<type>::iterator. <<
You mean std::vector<Dependency>::iterator or std::vector<Dependency>::const_iterator, right?

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Yes, you're right. Thank you.

I think the name 'isTrue' for a boolean variable is about the worst name you can get. How meaningful is it for itTrue to be true? What can we learn from isTrue being false?
What exactly is it that is, or is not, true? Now call it that instead!

Also, if you're doing many of these find operations on a vector then it's likely you'd be better off switching to another container instead such as a std::set.