vector of type template cass

This is a discussion on vector of type template cass within the C++ Programming forums, part of the General Programming Boards category; Hi all, Code: template <typename T> void FooFunc (vector< FooClass<T> > v) { vector < FooClass<T> >::iterator it; } I'm ...

  1. #1
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    vector of type template cass

    Hi all,

    Code:
    template <typename T>
    void
    FooFunc (vector< FooClass<T> > v)
    {
       vector < FooClass<T> >::iterator it;
      
    }
    I'm trying to do that, but I get an error, is this possible? If yes in which conditions? Do I have to give it a concrete class type like FooClass<float> ??

    The error says "expected ; before it"

    Thanks in advance.

  2. #2
    C++ Witch laserlight's Avatar
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    Yes, but here iterator is a name that depends on a template name: you know that it is a type name, but it could be say, a member name. You should use typename to disambiguate:
    Code:
    typename vector < FooClass<T> >::iterator it;
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
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    Oh, I really wasn't aware of this. Thank you for the explanation.

  4. #4
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    I have another doubt, how can I modify an element in vector and what is the best way to do it?
    See the example below, to see what I'm trying to do.

    Code:
    template <typename T>
    void
    FooFunc (vector< FooClass<T> > v)
    {
       vector < FooClass<T> >::iterator it;
       FooClass<T> tmp;
    
       for (it = v.begin(); it != v.end(); it++)
       {
          tmp = changeSomething(*it);
       }
      
       // How to replace the element??
       *it = tmp; // fails, because this will change the iterator.
      // Use copy or replace by having and temporary vector??
      // alternatives??
    }

  5. #5
    The larch
    Join Date
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    3,573
    I suppose you want:

    Code:
       for (it = v.begin(); it != v.end(); it++)
       {
          *it = changeSomething(*it);
       }
    Or perhaps:

    Code:
       std::transform(v.begin(), v.end(), v.begin(), changeSomething);
    It's likely that you don't want to pass a copy of the vector to FooFunc either.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  6. #6
    Registered User
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    Yes, you're correct, it should be passed by reference to avoid unnecessary copying.

    I will look into std::transform, thanks!

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