Editing Foreach loop (section)

=== C++ ===
[[C++11]] provides a foreach loop. The syntax is similar to that of [[Foreach loop#Java|Java]]:

<syntaxhighlight lang="Cpp">
#include <iostream>

int main()
{
  int myint[] = {1, 2, 3, 4, 5};

  for (int i : myint)
  {
    std::cout << i << '\n';
  }
}
</syntaxhighlight>

C++11 range-based for statements have been implemented in [[GNU Compiler Collection]] (GCC) (since version 4.6), [[Clang]] (since version 3.0) and [[Visual C++]] 2012 (version 11 <ref>{{cite web|url=http://blogs.msdn.com/b/vcblog/archive/2011/09/12/10209291.aspx |title=C++11 Features in Visual C++ 11 - Visual C++ Team Blog - Site Home - MSDN Blogs |publisher=Blogs.msdn.com |date=2011-09-12 |access-date=2013-08-04}}</ref>)

The range-based <code>for</code> is [[syntactic sugar]] equivalent to:

<syntaxhighlight lang="Cpp">
  for (auto __anon = begin(myint); __anon != end(myint); ++__anon)
  {
    auto i = *__anon;
    std::cout << i << '\n';
  }
</syntaxhighlight>

The compiler uses [[argument-dependent lookup]] to resolve the <code>begin</code> and <code>end</code> functions.<ref>{{cite web|url=https://en.cppreference.com/w/cpp/language/range-for |title=Range-based for loop (since C++11) |publisher=en.cppreference.com |access-date=2018-12-03}}</ref>

The [[C++ Standard Library]] also supports <code>for_each</code>,<ref>{{cite web|url=http://en.cppreference.com/w/cpp/algorithm/for_each |title=std::for_each - cppreference |publisher=en.cppreference.com |access-date=2017-09-30}}</ref> that applies each element to a function, which can be any predefined function or a lambda expression. While range-based for is only from the start to the end, the range or direction can be changed by altering the first two parameters.

<syntaxhighlight lang="Cpp">
#include <iostream>
#include <algorithm> // contains std::for_each
#include <vector>

int main()
{
  std::vector<int> v {1, 2, 3, 4, 5};

  std::for_each(v.begin(), v.end(), [](int i)
  {
    std::cout << i << '\n';
  });

  std::cout << "reversed but skip 2 elements:\n";

  std::for_each(v.rbegin()+2, v.rend(), [](int i)
  {
    std::cout << i << '\n';
  });
}
</syntaxhighlight>

[[Qt (software)|Qt]], a C++ framework, offers a macro providing foreach loops<ref>{{cite web |url=http://doc.qt.digia.com/4.2/containers.html#the-foreach-keyword |title=Qt 4.2: Generic Containers |publisher=Doc.qt.digia.com |access-date=2013-08-04 |archive-url=https://web.archive.org/web/20151123090839/http://doc.qt.digia.com/4.2/containers.html#the-foreach-keyword |archive-date=2015-11-23 |url-status=dead }}</ref> using the STL iterator interface:

<syntaxhighlight lang="Cpp">
#include <QList>
#include <QDebug>

int main()
{
  QList<int> list;

  list << 1 << 2 << 3 << 4 << 5;

  foreach (int i, list)
  {
    qDebug() << i;
  }
}</syntaxhighlight>

[[Boost (C++ libraries)|Boost]], a set of free peer-reviewed portable C++ libraries also provides foreach loops:<ref>{{cite web|author=Eric Niebler |url=http://www.boost.org/doc/libs/1_53_0/doc/html/foreach.html |title=Chapter 9. Boost.Foreach - 1.53.0 |publisher=Boost.org |date=2013-01-31 |access-date=2013-08-04}}</ref>

<syntaxhighlight lang="Cpp">
#include <boost/foreach.hpp>
#include <iostream>
 
int main()
{
  int myint[] = {1, 2, 3, 4, 5};
 
  BOOST_FOREACH(int &i, myint)
  {
    std::cout << i << '\n';
  }
}
</syntaxhighlight>