Add partitioning and sorting operations to libcpp.algorithm (GH-3202)

* Add is_partitioned and partition to libcpp.algorithm
* Add is_sorted and is_sorted_until to libcpp.algorithm
* Add partition_copy, stable_partition, and partition_point to libcpp.algorithm
* Move tests for sort and partial_sort into cpp_stl_algo_sorting_ops, add greater to libcpp.functional
* Add partial_sort_copy to libcpp.algorithm
* Add stable_sort to libcpp.algorithm
* Add nth_element to libcpp.algorithm
* Add missing except specifiers in libcpp.algorithm

Cython/Includes/libcpp/functional.pxd

+from libcpp cimport bool
+
 cdef extern from "<functional>" namespace "std" nogil:
     cdef cppclass function[T]:
         function() except +
@@ -10,4 +12,10 @@ cdef extern from "<functional>" namespace "std" nogil:
         function operator=(void*)
         function operator=[U](U)
 
-        bint operator bool()
+        bool operator bool()
+
+    # Comparisons
+    cdef cppclass greater[T=*]:
+        # https://github.com/cython/cython/issues/3193
+        greater() except +
+        bool operator()(const T& lhs, const T& rhs) except +

tests/run/cpp_stl_algo_partitioning_ops.pyx

+# mode: run
+# tag: cpp, werror, cpp11
+
+from __future__ import print_function
+
+from libcpp cimport bool
+from libcpp.algorithm cimport is_partitioned, partition, partition_copy, stable_partition, partition_point
+from libcpp.algorithm cimport for_each, copy, reverse
+from libcpp.iterator cimport back_inserter
+from libcpp.vector cimport vector
+
+
+cdef bool is_even(int i):
+    return i % 2 == 0
+
+
+def test_is_partitioned():
+    """
+    >>> test_is_partitioned()
+    False
+    True
+    False
+    """
+    cdef vector[int] values = range(10)
+    print(is_partitioned(values.begin(), values.end(), is_even))
+
+    partition(values.begin(), values.end(), &is_even)
+    print(is_partitioned(values.begin(), values.end(), is_even))
+
+    reverse(values.begin(), values.end())
+    print(is_partitioned(values.begin(), values.end(), is_even))
+
+
+cdef int print_int(int v) except -1:
+    print(v, end=" ")
+
+
+def print_partition(vector[int] values):
+    """
+    Test partition.
+
+    >> print_partition(range(10))
+    0 8 2 6 4  *  5 3 7 1 9
+    """
+    it = partition(values.begin(), values.end(), &is_even)
+    for_each(values.begin(), it, &print_int)
+    print("*", end=" ")
+    for_each(it, values.end(), &print_int)
+    print()
+
+
+def partition_ints_even(vector[int] values):
+    """
+    Test partition_copy.
+
+    >>> partition_ints_even(range(10))
+    ([0, 2, 4, 6, 8], [1, 3, 5, 7, 9])
+    """
+    cdef vector[int] even_values, odd_values
+    partition_copy(values.begin(), values.end(), back_inserter(even_values), back_inserter(odd_values), &is_even)
+    return even_values, odd_values
+
+
+cdef bool is_positive(int v):
+    return v > 0
+
+
+def partition_ints_positive(vector[int] values):
+    """
+    Test stable_partition.
+
+    >>> partition_ints_positive([0, 0, 3, 0, 2, 4, 5, 0, 7])
+    [3, 2, 4, 5, 7, 0, 0, 0, 0]
+    """
+    stable_partition(values.begin(), values.end(), &is_positive)
+    return values
+
+
+def partition_point_ints_even(vector[int] values):
+    """
+    Test partition_point.
+
+    >>> partition_point_ints_even([0, 8, 2, 6, 4, 5, 3, 7, 1, 9])
+    ([0, 8, 2, 6, 4], [5, 3, 7, 1, 9])
+    """
+    it = partition_point(values.begin(), values.end(), is_even)
+    cdef vector[int] even_values, odd_values
+    copy(values.begin(), it, back_inserter(even_values))
+    copy(it, values.end(), back_inserter(odd_values))
+    return even_values, odd_values

tests/run/cpp_stl_algo_sorting_ops.pyx

+# mode: run
+# tag: cpp, werror, cpp11
+
+from __future__ import print_function
+
+from libcpp cimport bool
+from libcpp.algorithm cimport is_sorted, is_sorted_until, sort, partial_sort, partial_sort_copy, stable_sort
+from libcpp.algorithm cimport nth_element
+from libcpp.functional cimport greater
+from libcpp.iterator cimport distance
+from libcpp.string cimport string
+from libcpp.vector cimport vector
+
+
+def is_sorted_ints(vector[int] values):
+    """
+    Test is_sorted.
+
+    >>> is_sorted_ints([3, 1, 4, 1, 5])
+    False
+    >>> is_sorted_ints([1, 1, 3, 4, 5])
+    True
+    """
+    return is_sorted(values.begin(), values.end())
+
+
+def initial_sorted_elements(vector[int] values):
+    """
+    Test is_sorted_until.
+
+    >>> initial_sorted_elements([4, 1, 9, 5, 1, 3])
+    1
+    >>> initial_sorted_elements([4, 5, 9, 3, 1, 1])
+    3
+    >>> initial_sorted_elements([9, 3, 1, 4, 5, 1])
+    1
+    >>> initial_sorted_elements([1, 3, 5, 4, 1, 9])
+    3
+    >>> initial_sorted_elements([5, 9, 1, 1, 3, 4])
+    2
+    >>> initial_sorted_elements([4, 9, 1, 5, 1, 3])
+    2
+    >>> initial_sorted_elements([1, 1, 4, 9, 5, 3])
+    4
+    """
+    sorted_end = is_sorted_until(values.begin(), values.end())
+    return distance(values.begin(), sorted_end)
+
+
+def sort_ints(vector[int] values):
+    """Test sort using the default operator<.
+
+    >>> sort_ints([5, 7, 4, 2, 8, 6, 1, 9, 0, 3])
+    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+    """
+    sort(values.begin(), values.end())
+    return values
+
+
+def sort_ints_reverse(vector[int] values):
+    """Test sort using a standard library comparison function object.
+
+    >>> sort_ints_reverse([5, 7, 4, 2, 8, 6, 1, 9, 0, 3])
+    [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
+    """
+    sort(values.begin(), values.end(), greater[int]())
+    return values
+
+
+def partial_sort_ints(vector[int] values, int k):
+    """
+    Test partial_sort using the default operator<.
+
+    >>> partial_sort_ints([4, 2, 3, 1, 5], 2)[:2]
+    [1, 2]
+    """
+    partial_sort(values.begin(), values.begin() + k, values.end())
+    return values
+
+
+def partial_sort_ints_reverse(vector[int] values, int k):
+    """
+    Test partial_sort using a standard library comparison function object.
+
+    >>> partial_sort_ints_reverse([4, 2, 3, 1, 5], 2)[:2]
+    [5, 4]
+    """
+    partial_sort(values.begin(), values.begin() + k, values.end(), greater[int]())
+    return values
+
+
+def partial_sort_ints2(vector[int] values, int k):
+    """
+    Test partial_sort_copy using the default operator<.
+
+    >>> partial_sort_ints2([4, 2, 3, 1, 5], 2)
+    [1, 2]
+    """
+    output = vector[int](2)
+    partial_sort_copy(values.begin(), values.end(), output.begin(), output.end())
+    return output
+
+
+def partial_sort_ints_reverse2(vector[int] values, int k):
+    """
+    Test partial_sort_copy using a standard library comparison function object.
+
+    >>> partial_sort_ints_reverse2([4, 2, 3, 1, 5], 2)
+    [5, 4]
+    """
+    output = vector[int](2)
+    partial_sort_copy(values.begin(), values.end(), output.begin(), output.end(), greater[int]())
+    return output
+
+
+cdef extern from *:
+    """
+    struct Employee
+    {
+        Employee() = default;
+        Employee(int age, std::string name): age(age), name(name) {}
+        int age;
+        std::string name;  // Does not participate in comparisons
+    };
+
+    bool operator<(const Employee& lhs, const Employee& rhs)
+    {
+        return lhs.age < rhs.age;
+    }
+    """
+    cppclass Employee:
+        Employee()
+        Employee(int, string)
+        int age
+        string name
+
+cdef bool Employee_greater(const Employee& lhs, const Employee& rhs):
+    return lhs.age > rhs.age
+
+def test_stable_sort():
+    """
+    Test stable_sort using cppreference example.
+
+    >>> test_stable_sort()
+    32, Arthur
+    108, Zaphod
+    108, Ford
+    108, Zaphod
+    108, Ford
+    32, Arthur
+    """
+    cdef vector[Employee] employees
+    employees.push_back(Employee(108, <string>b"Zaphod"))
+    employees.push_back(Employee(32, <string>b"Arthur"))
+    employees.push_back(Employee(108, <string>b"Ford"))
+
+    stable_sort(employees.begin(), employees.end())
+
+    for e in employees:
+        print("%s, %s" % (e.age, <str>(e.name).decode("ascii")))
+
+    stable_sort(employees.begin(), employees.end(), &Employee_greater)
+
+    for e in employees:
+        print("%s, %s" % (e.age, <str>(e.name).decode("ascii")))
+
+
+def second_smallest(vector[int] values):
+    """
+    Test nth_element using the default operator<.
+
+    >>> second_smallest([5, 6, 4, 3, 2, 6, 7, 9, 3])
+    3
+    """
+    nth_element(values.begin(), values.begin() + 1, values.end())
+    return values[1]
+
+
+def second_largest(vector[int] values):
+    """
+    Test nth_element using a standard library comparison function object.
+
+    >>> second_largest([5, 6, 4, 3, 2, 6, 7, 9, 3])
+    7
+    """
+    nth_element(values.begin(), values.begin() + 1, values.end(), greater[int]())
+    return values[1]

tests/run/libcpp_algo.pyx

@@ -2,7 +2,7 @@
 # tag: cpp
 
 from libcpp cimport bool
-from libcpp.algorithm cimport make_heap, sort_heap, sort, partial_sort
+from libcpp.algorithm cimport make_heap, sort_heap
 from libcpp.vector cimport vector
 
 
@@ -28,33 +28,3 @@ def heapsort(l, bool reverse=False):
         sort_heap(v.begin(), v.end())
 
     return v
-
-
-def partialsort(l, int k, reverse=False):
-    """
-    >>> partialsort([4, 2, 3, 1, 5], k=2)[:2]
-    [1, 2]
-    >>> partialsort([4, 2, 3, 1, 5], k=2, reverse=True)[:2]
-    [5, 4]
-    """
-    cdef vector[int] v = l
-    if reverse:
-        partial_sort(v.begin(), v.begin() + k, v.end(), &greater)
-    else:
-        partial_sort(v.begin(), v.begin() + k, v.end())
-    return v
-
-
-def stdsort(l, reverse=False):
-    """
-    >>> stdsort([3, 2, 1, 4, 5])
-    [1, 2, 3, 4, 5]
-    >>> stdsort([3, 2, 1, 4, 5], reverse=True)
-    [5, 4, 3, 2, 1]
-    """
-    cdef vector[int] v = l
-    if reverse:
-        sort(v.begin(), v.end(), &greater)
-    else:
-        sort(v.begin(), v.end())
-    return v