add doc: Heap operation

docs/_sources/libs/sprout/algorithm/index.txt

@@ -37,6 +37,8 @@ Sprout.Algorithm
     upper_bound
     equal_range
     binary_search
+    is_heap
+    is_heap_until
 
 .. _sprout-algorithm-non_modifying:
 *******************************************************************************

docs/_sources/libs/sprout/algorithm/is_heap.txt

@@ -0,0 +1,46 @@
+.. _sprout-algorithm-is_heap:
+###############################################################################
+is_heap
+###############################################################################
+
+Interface
+========================================
+.. sourcecode:: c++
+
+  template<typename RandomAccessIterator>
+  inline SPROUT_CONSTEXPR bool
+  is_heap(RandomAccessIterator first, RandomAccessIterator last);
+  
+  template<typename RandomAccessIterator, typename Compare>
+  inline SPROUT_CONSTEXPR bool
+  is_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
+
+Returns
+========================================
+
+| ``is_heap_until(first, last) == last``, ``is_heap_until(first, last, comp) == last``
+
+Examples
+========================================
+.. sourcecode:: c++
+
+  #include <sprout/algorithm/is_heap.hpp>
+  #include <sprout/array.hpp>
+  #include <sprout/container.hpp>
+  using namespace sprout;
+
+  SPROUT_STATIC_CONSTEXPR auto input = array<int, 10>{{10, 9, 8, 6, 7, 2, 5, 3, 4, 1}};
+  SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap(begin(input), end(input));
+  static_assert(result, "input is a heap.");
+
+Complexity
+========================================
+
+| Recursive function invocations in *O(logN)* (logarithmic) depth.
+
+Header
+========================================
+
+| ``sprout/algorithm/is_heap.hpp``
+| Convenience header: ``sprout/algorithm.hpp``
+

docs/_sources/libs/sprout/algorithm/is_heap_until.txt

@@ -0,0 +1,48 @@
+.. _sprout-algorithm-is_heap_until:
+###############################################################################
+is_heap_until
+###############################################################################
+
+Interface
+========================================
+.. sourcecode:: c++
+
+  template<typename RandomAccessIterator>
+  inline SPROUT_CONSTEXPR RandomAccessIterator
+  is_heap_until(RandomAccessIterator first, RandomAccessIterator last);
+  
+  template<typename RandomAccessIterator, typename Compare>
+  inline SPROUT_CONSTEXPR RandomAccessIterator
+  is_heap_until(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
+
+Returns
+========================================
+
+| If ``distance(first, last) < 2``, returns last.
+| Otherwise, returns the last iterator i in [first,last] for which the range [first,i) is a heap.
+
+Examples
+========================================
+.. sourcecode:: c++
+
+  #include <sprout/algorithm/is_heap_until.hpp>
+  #include <sprout/array.hpp>
+  #include <sprout/container.hpp>
+  using namespace sprout;
+
+  SPROUT_STATIC_CONSTEXPR auto input = array<int, 10>{{10, 9, 8, 6, 7, 2, 5, 13, 14, 11}};
+  SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap_until(begin(input), end(input));
+  static_assert(result - begin(input) == 7, "input is a heap until position 7.");
+
+Complexity
+========================================
+
+| Linear.
+| Recursive function invocations in *O(logN)* (logarithmic) depth.
+
+Header
+========================================
+
+| ``sprout/algorithm/is_heap_until.hpp``
+| Convenience header: ``sprout/algorithm.hpp``
+