From a4659b9fa68127689b2bac52f82d373efee5e0f2 Mon Sep 17 00:00:00 2001
From: John Omotani <john.omotani@ukaea.uk>
Date: Fri, 23 Aug 2024 16:38:07 +0100
Subject: [PATCH] Do linear extrapolation in PsiContour.contourSfunc()

This allows the 'orthogonal' Sfunc to do something sensible at the
targets when it is being used there because only the X-point is
'nonorthogonal'.
---
 hypnotoad/core/equilibrium.py | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/hypnotoad/core/equilibrium.py b/hypnotoad/core/equilibrium.py
index f69fb0f0..6701549a 100644
--- a/hypnotoad/core/equilibrium.py
+++ b/hypnotoad/core/equilibrium.py
@@ -1697,8 +1697,11 @@ def contourSfunc(self, *, psi, kind="cubic"):
             i,
             [i <= 0.0, i >= thisEndInd - thisStartInd],
             [
-                0.0,
-                endDistance - startDistance,
+                lambda i: i * (distance[thisStartInd + 1] - distance[thisStartInd]),
+                lambda i: endDistance
+                - startDistance
+                + (i - thisEndInd + thisStartInd)
+                * (distance[thisEndInd] - distance[thisEndInd - 1]),
                 lambda i: interpS(i + thisStartInd) - startDistance,
             ],
         )