STLAlgorithmExtensions/IsSortedFunction

Too bad it isn' t in the C++ std.

It does exist in stl. One can use "adjacent_find" with predicate "less" to obtain the same result

Container container; // e.g. typedef vector<int> Container;
...

if (adjacent_find(container.begin(),container.end(),greater<Container::value_type>())==container.end())
  ...; // container is sorted

Of course, greater (i.e. operator>() ) may not be defined for the type in question. In any case, here is the is_sorted duo:

template <class ForwardIterator>
bool is_sorted(ForwardIterator first, ForwardIterator last)
{
  if (first!=last)
    for (ForwardIterator it(first++);first!=last;++it /* or it=first */,++first)
      if (*first<*it)
        return false;

  return true;
}

template <class ForwardIterator, class Predicate>
bool is_sorted(ForwardIterator first, ForwardIterator last,
               Predicate pred)
{
  if (first!=last)
    for (ForwardIterator it(first++);first!=last;++it /* or it=first */,++first)
      if (!pred(*it,*first))
        return false;

  return true;
}

If anyone finds bugs or can improve performance, please do so...

Container container; // e.g. typedef vector<Foo> Container;
...

if (adjacent_find(container.rbegin(),container.rend(),less<Container::value_type>())==container.rend())
  ...; // container is sorted