STL algorithm all or any function?

Question

Is there anything approximating Haskell's all or any functions as part of the STL? If not, is the below a good implementation (I noticed the sgi STL performed partial specialization if the iterators were random access, though I have not bothered with this)?

template <typename InputIterator, typename Predicate>
inline bool all(InputIterator first, InputIterator last, Predicate pred) {
  while (first != last) {
    if (!pred(*first)) {
      return false;
    }
    ++first;
  }
  return true;
}

Similarly, how would this best be transformed to iterate two sequences, and return true where a BinaryPredicate returns true for all, and false otherwise? I know this is relatively trivial, but it seems like this should be provided by algorithm, and I want to make sure I'm not overlooking something.

Answer 1

There are not all or any algorithms in C++ currently, but C++0x adds std::all_of and std::any_of algorithms to the C++ standard library. Your implementation may support these already.

Since both of these algorithms need to test every element in the range (at least until they find a match or mismatch), there isn't any reason to specialize them for different types of iterators: the performance when used with forward iterators should be the same as the performance when used with random access iterators.

Your implementation of all is fine; the Visual C++ all_of implementation is effectively the same, except that it uses a for loop instead of a while loop.

how would this best be transformed to iterate two sequences, and return true where a BinaryPredicate returns true for all, and false otherwise?

This is what std::equal does. You'll need to check the sizes of the ranges first to ensure that they are of the same size.

Answer 2

You can use std::find_if like, which returns Iterator last if the predicate returns false for all elements, otherwise it returns the element that it returns true for.

Iterator it = std::find_if (container.begin (), container.end (), predicate);
if (it != container.end ())
    // One of them doesn't match

Answer 3

This looks almost equivalent to std::find_if with the predicate inverted to me.

Answer 4

How about foreach from BOOST ? it's not STL but available for any platform.