diff --git a/linq/core/collections.py b/linq/core/collections.py
index d4dc8af..03e84e1 100644
--- a/linq/core/collections.py
+++ b/linq/core/collections.py
@@ -1,27 +1,44 @@
-class Generator:
-    def __init__(self, rule, start_elem):
-        self.rule = rule
-        self.start_elem = start_elem
+class Deducer:
+    def __init__(self, first, rest=None):
+        self.first = first
+        self.rest = rest or (lambda: Deducer(None, None))
 
-    def __iter__(self):
-        now = self.start_elem
-        while True:
-            try:
-                yield now
-                now = self.rule(now)
-            except StopIteration:
-                break
+    @classmethod
+    def determine(cls, *values):
+        if not values:
+            return cls(None, None)
+
+        return cls(values[0], lambda: cls.determine(*values[1:]))
 
+    @classmethod
+    def deduce(cls, f, *initializer):
+        return cls(initializer[0], lambda: cls.deduce(f, *(initializer[1:] + (f(*initializer),))))
 
-class ScanGenerator:
-    def __init__(self, rule, seq, start_elem):
-        self.rule = rule
-        self.seq = seq
-        self.start_elem = start_elem
+    @classmethod
+    def scan(cls, rule, seq, start_elem):
+        try:
+            iterator = iter(seq)
+            last = start_elem
+            now = rule(last, next(iterator))
+            return cls(now, lambda: cls.scan(rule, iterator, now))
+        except StopIteration:
+            return cls(None, None)
+
+    def __radd__(self, left):
+        return Deducer(left, lambda: self.determine(self.first, *self.rest()))
 
     def __iter__(self):
-        last = self.start_elem
-        for now in self.seq:
-            acc = self.rule(last, now)
-            yield acc
-            last = acc
+        try:
+            if self.first is None:
+                raise StopIteration
+            yield self.first
+            yield from self.rest()
+        except StopIteration:
+            pass
+
+    def __next__(self):
+        if self.first is None:
+            raise StopIteration
+        now, nex = self.first, self.rest()
+        self.first, self.rest = nex.first, nex.rest
+        return now
diff --git a/linq/standard/general.py b/linq/standard/general.py
index ef4c6b9..1276d0c 100644
--- a/linq/standard/general.py
+++ b/linq/standard/general.py
@@ -1,4 +1,4 @@
-from ..core.collections import ScanGenerator
+from ..core.collections import Deducer
 from ..core.flow import *
 from ..core.utils import *
 from functools import reduce
@@ -49,12 +49,12 @@ def Then(self: object, f):
 
 @extension_std
 def Scan(self: Iterable, f, start_elem):
-    return ScanGenerator(f, self, start_elem)
+    return Deducer.scan(f, self, start_elem)
 
 
 @extension_std
 def Reduce(self: Iterable, f, start_elem=None):
-    return reduce(f, self) if start_elem is None else reduce(f, self)
+    return reduce(f, self) if start_elem is None else reduce(f, self, start_elem)
 
 
 @extension_std
diff --git a/linq/standard/generator.py b/linq/standard/generator.py
index 6f572ca..7bc14ad 100644
--- a/linq/standard/generator.py
+++ b/linq/standard/generator.py
@@ -1,3 +1,4 @@
+from ..core.collections import *
 from ..core.flow import *
 from sys import version_info
 
diff --git a/test_manual.py b/test_manual.py
index 8b6fec1..29ba324 100644
--- a/test_manual.py
+++ b/test_manual.py
@@ -1,6 +1,6 @@
 # see the standard library to get all the extension methods.
 
-from linq.core.collections import Generator as MGenerator
+from linq.core.collections import Deducer
 from linq import Flow, extension_class, extension_class_name
 
 
@@ -12,7 +12,7 @@ def block_lambda(e):
         else:
             raise StopIteration
 
-    res = Flow(MGenerator(block_lambda, 0)).Take(100).ToList()
+    res = Flow(Deducer.deduce(block_lambda, 0)).Take(100).ToList()
 
     assert res.__str__() == res.__repr__()
 
@@ -23,7 +23,7 @@ def block_lambda(e):
 def my_test(func):
     def call():
         global seq
-        seq = Flow(MGenerator(lambda x: x + 1, start_elem=0))  # [0..\infty]
+        seq = Flow(Deducer.deduce(lambda x: x + 1, 0))  # [0..\infty]
         func.__globals__['seq'] = seq
         func()
 
@@ -35,8 +35,6 @@ def test_example1():
     # See the definition of MGenerator at https://github.com/thautwarm/ActualFn.py/blob/master/linq/core/collections.py.
     # It's a generalization of PyGenerator.
     # What's more, it can be deepcopid and serialized!
-
-
     """
     Example 1:
     """
@@ -162,3 +160,23 @@ def MyNext(self):
 
 test_extension_byclsname()
 Flow((i for i in range(10))).MyNext()
+
+
+"""
+Example 6:
+"""
+deducer_seq1 = Deducer.determine(1, 2, 3, 4, 5)
+print(list(deducer_seq1))
+# => [1, 2, 3, 4, 5]
+
+deducer_seq2 = Deducer.deduce(lambda x: x + 1, 0)
+print([e for (e, _) in zip(deducer_seq2, range(10))])
+# => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+
+deducer_seq3 = Deducer.deduce(lambda x, y: x + y, 1, 1)
+print([e for (e, _) in zip(deducer_seq3, range(10))])
+# => [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
+
+deducer_seq4 = Deducer.scan(lambda x, y: x + y, deducer_seq2, 10)
+print([e for (e, _) in zip(deducer_seq4, range(10))])
+# => [10, 11, 13, 16, 20, 25, 31, 38, 46, 55]
\ No newline at end of file