add support for C++ stdlib heap operations

CHANGES.rst

@@ -47,6 +47,8 @@ Features added
 
 * Defines dynamic_cast et al. in `libcpp.cast`.
 
+* Support for C++ heap data structure operations (from ``<algorithm>``).
+
 Optimizations
 -------------
 

Cython/Includes/libcpp/algorithm.pxd

+cdef extern from "<algorithm>" namespace "std" nogil:
+    void make_heap[Iter](Iter first, Iter last)
+    void make_heap[Iter, Compare](Iter first, Iter last, Compare comp)
+
+    void pop_heap[Iter](Iter first, Iter last)
+    void pop_heap[Iter, Compare](Iter first, Iter last, Compare comp)
+
+    void push_heap[Iter](Iter first, Iter last)
+    void push_heap[Iter, Compare](Iter first, Iter last, Compare comp)
+
+    void sort_heap[Iter](Iter first, Iter last)
+    void sort_heap[Iter, Compare](Iter first, Iter last, Compare comp)

tests/run/libcpp_algo.pyx

+# tag: cpp
+
+from libcpp cimport bool
+from libcpp.algorithm cimport make_heap, sort_heap
+from libcpp.vector cimport vector
+
+
+# XXX should use std::greater, but I don't know how to wrap that.
+cdef inline bool greater(int x, int y):
+    return x > y
+
+
+def heapsort(l, bool reverse=False):
+    """
+    >>> heapsort([3, 5, 1, 0, 2, 4])
+    [0, 1, 2, 3, 4, 5]
+    >>> heapsort([3, 5, 1, 0, 2, 4], reverse=True)
+    [5, 4, 3, 2, 1, 0]
+    """
+    cdef vector[int] v = l
+
+    if reverse:
+        make_heap(v.begin(), v.end(), greater)
+        sort_heap(v.begin(), v.end(), greater)
+    else:
+        make_heap(v.begin(), v.end())
+        sort_heap(v.begin(), v.end())
+
+    return v