From 181a8e762191f5f9cab774247c8825146486cbba Mon Sep 17 00:00:00 2001
From: Martin Bauer <bauer_martin@gmx.de>
Date: Mon, 23 Jan 2017 13:57:17 +0100
Subject: [PATCH] new lbmpy: boundaries
---
sympyextensions.py | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/sympyextensions.py b/sympyextensions.py
index dc5a0073b..a5121775f 100644
--- a/sympyextensions.py
+++ b/sympyextensions.py
@@ -356,3 +356,14 @@ def commonDenominator(expr):
denominators = [r.q for r in expr.atoms(sp.Rational)]
return sp.lcm(denominators)
+
+def getSymmetricPart(term, vars):
+ """
+ Returns the symmetric part of a sympy expressions.
+
+ :param term: sympy expression, labeled here as :math:`f`
+ :param vars: sequence of symbols which are considered as degrees of freedom, labeled here as :math:`x_0, x_1,...`
+ :returns: :math:`\frac{1}{2} [ f(x_0, x_1, ..) + f(-x_0, -x_1) ]`
+ """
+ substitutionDict = {e: -e for e in vars}
+ return sp.Rational(1, 2) * (term + fastSubs(term, substitutionDict))
--
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