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Are the non-member function templates begin(container) and end(container) part of C++0x? If so, in which header file do they live?

fredoverflow
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1 Answers1

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Yes, but just as swap is defined in different places and depends on ADL, so are begin and end. The 'generic' versions are defined in <iterator>:

// 24.6.5, range access:
template <class C> auto begin(C& c) -> decltype(c.begin());
template <class C> auto begin(const C& c) -> decltype(c.begin());
template <class C> auto end(C& c) -> decltype(c.end());
template <class C> auto end(const C& c) -> decltype(c.end());
template <class T, size_t N> T* begin(T (&array)[N]);
template <class T, size_t N> T* end(T (&array)[N]);

Note also that 24.6.5 says:

In addition to being available via inclusion of the <iterator> header, the function templates in 24.6.5 are available when any of the following headers are included: <array>, <deque>, <forward_list>, <list>, <map>, <regex>, <set>, <string>, <unordered_map>, <unordered_set>, and <vector>.

Yakov Galka
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  • Out of sheer curiosity: Why would someone use them instead of `c.begin()`? – Karl von Moor Jul 30 '11 at 11:03
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    @Karl because that's not possible for all types you can iterate over. That if `c` is an array. – Johannes Schaub - litb Jul 30 '11 at 11:10
  • @Karl: although the prefix syntax becomes unreadable when chained (`f(g(h(x)), a(b(y)))`), it's extensible and looks much more like functional programming. It only remains to add open multi-methods to the language. – Yakov Galka Jul 30 '11 at 12:02
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    @Karl: Atop of what Johannes and ybungalobill said: Every C++ programmer (especially those coming from Java, C# and the like) should have read [this classic article](http://drdobbs.com/184401197) by Scott Meyers. – sbi Jul 30 '11 at 12:49
  • @Karl: For a situation where global begin/end are indispensable, see the [pretty printer](http://louisdx.github.com/cxx-prettyprint/), or [STL #6](http://channel9.msdn.com/Shows/Going+Deep/C9-Lectures-Stephan-T-Lavavej-Advanced-STL-6-of-n) (from where I got the idea). – Kerrek SB Jul 30 '11 at 14:22