From b416e4864cc492caf9062a2ad0f55c9b6a885808 Mon Sep 17 00:00:00 2001
From: Christoph Groth <christoph.groth@cea.fr>
Date: Wed, 26 Sep 2018 11:56:13 +0200
Subject: [PATCH] expand whatsnew item about defaults values being no longer
 allowed

---
 doc/source/pre/whatsnew/1.4.rst | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/doc/source/pre/whatsnew/1.4.rst b/doc/source/pre/whatsnew/1.4.rst
index e7674772..42b6b5c5 100644
--- a/doc/source/pre/whatsnew/1.4.rst
+++ b/doc/source/pre/whatsnew/1.4.rst
@@ -6,8 +6,8 @@ See also the `full list of changes up to the most recent bugfix
 release of the 1.4 series
 <https://gitlab.kwant-project.org/kwant/kwant/compare/v1.4.0...latest-1.4>`_.
 
-Value functions no longer accept default values for parameters
---------------------------------------------------------------
+Value functions may no longer have default values for parameters
+----------------------------------------------------------------
 Using value functions with default values for parameters can be
 problematic, especially when re-using value functions between simulations.
 When parameters have default values it is easy to forget that such a
@@ -35,6 +35,16 @@ Concretely, the above means that the following no longer works::
   # Raises ValueError
   syst = syst.finalized()
 
+As a solution, simply remove the default values and always provide ``t``.
+To deal with many parameters, the following idiom may be useful::
+
+  defaults = dict(a=0, b=1, c=2, d=3)
+  ...
+  smatrix = kwant.smatrix(syst, E, params=dict(defaults, d=4, e=5))
+
+Note that it allows to override defaults as well as to add additional
+parameters.
+
 System parameter substitution
 -----------------------------
 After the introduction of ``Builder.fill`` it has become possible to construct
-- 
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