--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/symbian-qemu-0.9.1-12/python-2.6.1/Demo/classes/Range.py	Fri Jul 31 15:01:17 2009 +0100
@@ -0,0 +1,93 @@
+"""Example of a generator: re-implement the built-in range function
+without actually constructing the list of values.
+
+OldStyleRange is coded in the way required to work in a 'for' loop before
+iterators were introduced into the language; using __getitem__ and __len__ .
+
+"""
+def handleargs(arglist):
+    """Take list of arguments and extract/create proper start, stop, and step
+    values and return in a tuple"""
+    try:
+        if len(arglist) == 1:
+            return 0, int(arglist[0]), 1
+        elif len(arglist) == 2:
+            return int(arglist[0]), int(arglist[1]), 1
+        elif len(arglist) == 3:
+            if arglist[2] == 0:
+                raise ValueError("step argument must not be zero")
+            return tuple(int(x) for x in arglist)
+        else:
+            raise TypeError("range() accepts 1-3 arguments, given", len(arglist))
+    except TypeError:
+        raise TypeError("range() arguments must be numbers or strings "
+        "representing numbers")
+
+def genrange(*a):
+    """Function to implement 'range' as a generator"""
+    start, stop, step = handleargs(a)
+    value = start
+    while value < stop:
+        yield value
+        value += step
+
+class oldrange:
+    """Class implementing a range object.
+    To the user the instances feel like immutable sequences
+    (and you can't concatenate or slice them)
+
+    Done using the old way (pre-iterators; __len__ and __getitem__) to have an
+    object be used by a 'for' loop.
+
+    """
+
+    def __init__(self, *a):
+        """ Initialize start, stop, and step values along with calculating the
+        nubmer of values (what __len__ will return) in the range"""
+        self.start, self.stop, self.step = handleargs(a)
+        self.len = max(0, (self.stop - self.start) // self.step)
+
+    def __repr__(self):
+        """implement repr(x) which is also used by print"""
+        return 'range(%r, %r, %r)' % (self.start, self.stop, self.step)
+
+    def __len__(self):
+        """implement len(x)"""
+        return self.len
+
+    def __getitem__(self, i):
+        """implement x[i]"""
+        if 0 <= i <= self.len:
+            return self.start + self.step * i
+        else:
+            raise IndexError, 'range[i] index out of range'
+
+
+def test():
+    import time, __builtin__
+    #Just a quick sanity check
+    correct_result = __builtin__.range(5, 100, 3)
+    oldrange_result = list(oldrange(5, 100, 3))
+    genrange_result = list(genrange(5, 100, 3))
+    if genrange_result != correct_result or oldrange_result != correct_result:
+        raise Exception("error in implementation:\ncorrect   = %s"
+                         "\nold-style = %s\ngenerator = %s" %
+                         (correct_result, oldrange_result, genrange_result))
+    print "Timings for range(1000):"
+    t1 = time.time()
+    for i in oldrange(1000):
+        pass
+    t2 = time.time()
+    for i in genrange(1000):
+        pass
+    t3 = time.time()
+    for i in __builtin__.range(1000):
+        pass
+    t4 = time.time()
+    print t2-t1, 'sec (old-style class)'
+    print t3-t2, 'sec (generator)'
+    print t4-t3, 'sec (built-in)'
+
+
+if __name__ == '__main__':
+    test()