From e602b032302b5f3106d898eb01ed178f8451b155 Mon Sep 17 00:00:00 2001
From: Christoph Groth <christoph.groth@cea.fr>
Date: Fri, 13 Jul 2012 15:14:13 +0200
Subject: [PATCH] tutorial: introduce function objects in a gentler way
---
doc/source/tutorial/tutorial2.rst | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)
diff --git a/doc/source/tutorial/tutorial2.rst b/doc/source/tutorial/tutorial2.rst
index 236e980a..eba8cc01 100644
--- a/doc/source/tutorial/tutorial2.rst
+++ b/doc/source/tutorial/tutorial2.rst
@@ -244,31 +244,27 @@ oscillatory transmission behavior through resonances in the quantum well.
In this case, `g()` always uses the local variable inside `f()`
(unless we would add ``global string`` in `g()`).
- - `~kwant.builder.Builder` does not only accept functions as
- values, but every python object that can be used as a function.
+ - `~kwant.builder.Builder` in fact accepts not only functions but any python
+ object which is callable. We can take advantage of the fact that instances
+ of python classes with a `__call__` method can be called just as if they
+ were functions::
- In particular it allows to use a functor::
-
- class Functor:
- def __init__(self, x1, x2):
- self.x1 = x1
- self.x2 = x2
+ class Well:
+ def __init__(self, a, b=0):
+ self.a = a
+ self.b = b
def __call__(self, site):
x, y = site.pos
- if self.x1 < x < self.x2:
- return self.pot
- else:
- return 0
+ return self.a * (x**2 + y**2) + b
- functor = Functor(10, 20)
+ well = Well(3, 4)
- sys[...] = functor
+ sys[...] = well
- functor.pot = ...
+ well.a = ...
- This approach would in principle also avoid the use of
- a global variable, as the value of the potential could
+ This approach allows to avoid the use of global variables. Parameters can
be changed inside the object.
.. _tutorial-abring:
--
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