Programming Forums > Application Development > C++

titaniumdecoy · Jul 2nd, 2008, 10:47 PM

I want to write a function that takes the begin() and end() values returned by an iterator like many STL functions. I am not sure what type the arguments should be. Is it necessary to use templates? For example:

(Toggle Plain Text)

// function definition - what is type?
void myfunc(type a, type b) { ... }

int main() {
    ...
    vector<double>::iterator iter = ...;
    myfunc(iter.begin(), iter.end());
}

I want to be able to pass any type of iterator, such as list<string>::iterator.

titaniumdecoy · Jul 3rd, 2008, 12:43 AM

I have done some searching, and it seems that templates are the way to go. So:

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template <typename ForwardIter>
void myfunc(ForwardIter begin, ForwardIter end) { ... }

However, I have also found a number of pre-defined iterator types such as forward_iterator, backward_iterator, etc. How can I use these rather than templates?

grumpy · Jul 3rd, 2008, 5:21 AM

Assuming you have a standard container, the type of its iterators are of the form std::container<TYPE>::iterator_type (where container = vector, list, etc, TYPE is the type of element, and iterator_type = iterator, const_iterator, etc).

You also need to be aware that begin(), end(), rbegin(), rend(), etc are - depending on type of container - often overloaded: for example has a std::vector<>::begin() that returns an iterator and another that returns a const_iterator (and possibly other types of iterator, I haven't checked).

titaniumdecoy · Jul 3rd, 2008, 12:11 PM

How can I ensure that the arguments to the function above are of iterator_type = forward_iterator?

grumpy · Jul 4th, 2008, 4:05 AM

Declare/define your function myfunc() with arguments of type std::container<TYPE>::forward_iterator, and do not overload it for other types. If you attempt to call it with arguments of types other than forward_iterator (or, more precisely, of types that are not implicitly convertible to forward_iterator - which is possibly compiler dependent) you will obtain a compilation error.

Jul 2nd, 2008, 10:47 PM	#1
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 856 Rep Power: 3	Library function-like implementation I want to write a function that takes the begin() and end() values returned by an iterator like many STL functions. I am not sure what type the arguments should be. Is it necessary to use templates? For example: (Toggle Plain Text) // function definition - what is type? void myfunc(type a, type b) { ... } int main() { ... vector<double>::iterator iter = ...; myfunc(iter.begin(), iter.end()); } // function definition - what is type? void myfunc(type a, type b) { ... } int main() { ... vector<double>::iterator iter = ...; myfunc(iter.begin(), iter.end()); } I want to be able to pass any type of iterator, such as list<string>::iterator.

Jul 3rd, 2008, 12:43 AM	#2
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 856 Rep Power: 3	Re: Library function implementation I have done some searching, and it seems that templates are the way to go. So: (Toggle Plain Text) template <typename ForwardIter> void myfunc(ForwardIter begin, ForwardIter end) { ... } template <typename ForwardIter> void myfunc(ForwardIter begin, ForwardIter end) { ... } However, I have also found a number of pre-defined iterator types such as forward_iterator, backward_iterator, etc. How can I use these rather than templates?

Jul 3rd, 2008, 5:21 AM	#3
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,223 Rep Power: 5	Re: Library function implementation Assuming you have a standard container, the type of its iterators are of the form std::container<TYPE>::iterator_type (where container = vector, list, etc, TYPE is the type of element, and iterator_type = iterator, const_iterator, etc). You also need to be aware that begin(), end(), rbegin(), rend(), etc are - depending on type of container - often overloaded: for example has a std::vector<>::begin() that returns an iterator and another that returns a const_iterator (and possibly other types of iterator, I haven't checked).

Jul 3rd, 2008, 12:11 PM	#4
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 856 Rep Power: 3	Re: Library function implementation How can I ensure that the arguments to the function above are of iterator_type = forward_iterator?

Jul 4th, 2008, 4:05 AM	#5
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,223 Rep Power: 5	Re: Library function implementation Declare/define your function myfunc() with arguments of type std::container<TYPE>::forward_iterator, and do not overload it for other types. If you attempt to call it with arguments of types other than forward_iterator (or, more precisely, of types that are not implicitly convertible to forward_iterator - which is possibly compiler dependent) you will obtain a compilation error.

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Programming Forums > Application Development > C++

Library function implementation