From d16afb8e2be4c1add9f7b60958770e44215d5252 Mon Sep 17 00:00:00 2001
From: Christoph Groth <christoph.groth@cea.fr>
Date: Tue, 11 Apr 2017 18:36:09 +0200
Subject: [PATCH] clarify to_fd()
---
kwant/builder.py | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/kwant/builder.py b/kwant/builder.py
index 777cbe1f..751e801e 100644
--- a/kwant/builder.py
+++ b/kwant/builder.py
@@ -282,6 +282,11 @@ class Symmetry(metaclass=abc.ABCMeta):
is used together with sites whose site family is not compatible with it. A
typical example of this is when the vector defining a translational
symmetry is not a lattice vector.
+
+ The type of the domain objects as handled by the methods of this class is
+ not specified. The only requirement is that it must support the unary
+ minus operation. The reference implementation of `to_fd()` is hence
+ `self.act(-self.which(a), a, b)`.
"""
@abc.abstractproperty
@@ -306,12 +311,11 @@ class Symmetry(metaclass=abc.ABCMeta):
def to_fd(self, a, b=None):
"""Map a site or hopping to the fundamental domain.
- If ``b`` is None, return a site equivalent to ``a`` within the fundamental
- domain. Otherwise, return a hopping equivalent to ``(a, b)`` but where
- the first element belongs to the fundamental domain.
-
- This default implementation works but may be not efficient.
+ If ``b`` is None, return a site equivalent to ``a`` within the
+ fundamental domain. Otherwise, return a hopping equivalent to ``(a,
+ b)`` but where the first element belongs to the fundamental domain.
+ Equivalent to `self.act(-self.which(a), a, b)`.
"""
return self.act(-self.which(a), a, b)
--
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