Merge branch 't/13580/map_reduce' into 13580

src/doc/en/reference/combinat/module_list.rst

@@ -122,6 +122,7 @@ Comprehensive Module list
     sage/combinat/kazhdan_lusztig
     sage/combinat/knutson_tao_puzzles
     sage/combinat/lyndon_word
+    sage/combinat/map_reduce
     sage/combinat/matrices/__init__
     sage/combinat/matrices/all
     sage/combinat/matrices/dancing_links

src/sage/combinat/backtrack.py

@@ -427,6 +427,8 @@ def __init__(self, roots = None, children = None, post_process = None,
         self._algorithm = algorithm
         Parent.__init__(self, facade = facade, category = EnumeratedSets().or_subcategory(category))
 
+    __len__ = None
+
     def _repr_(self):
         r"""
         TESTS::
@@ -717,6 +719,30 @@ def __contains__(self, elt):
             stack.append( iter(self.children(node)) )
         return False
 
+    def map_reduce(self, map_function = None,
+                   reduce_function = None,
+                   reduce_init = None):
+        r"""
+        Apply en Map Reduce algorithm on ``self``
+
+        EXAMPLES::
+
+            sage: F = SearchForest( [([i],i, i) for i in range(1,10)],
+            ...     lambda (list, sum, last):
+            ...         [(list + [i], sum + i, i) for i in range(1,last)],
+            ...     lambda x: x)
+            sage: y = var('y')
+            sage: F.map_reduce(
+            ...    lambda (li, sum, _): y**sum, lambda x,y: x + y,  0 )
+            y^45 + y^44 + y^43 + 2*y^42 + 2*y^41 + 3*y^40 + 4*y^39 + 5*y^38 + 6*y^37 + 8*y^36 + 9*y^35 + 10*y^34 + 12*y^33 + 13*y^32 + 15*y^31 + 17*y^30 + 18*y^29 + 19*y^28 + 21*y^27 + 21*y^26 + 22*y^25 + 23*y^24 + 23*y^23 + 23*y^22 + 23*y^21 + 22*y^20 + 21*y^19 + 21*y^18 + 19*y^17 + 18*y^16 + 17*y^15 + 15*y^14 + 13*y^13 + 12*y^12 + 10*y^11 + 9*y^10 + 8*y^9 + 6*y^8 + 5*y^7 + 4*y^6 + 3*y^5 + 2*y^4 + 2*y^3 + y^2 + y
+        """
+        from sage.combinat.map_reduce import SearchForestMapReduce
+        return SearchForestMapReduce(forest = self,
+                                     map_function = map_function,
+                                     reduce_function = reduce_function,
+                                     reduce_init = reduce_init).run()
+
+
 class PositiveIntegerSemigroup(UniqueRepresentation, SearchForest):
     r"""
     The commutative additive semigroup of positive integers.

src/sage/combinat/enumerated_sets.py

@@ -119,6 +119,7 @@
 
 - :func:`~sage.sets.recursively_enumerated_set.RecursivelyEnumeratedSet`
 - :class:`~sage.combinat.backtrack.GenericBacktracker`
+- :ref:`sage.combinat.map_reduce`
 - :ref:`sage.combinat.tiling`
 - :ref:`sage.combinat.dlx`
 - :ref:`sage.combinat.matrices.dlxcpp`