From c7f56127179a188cde40214a02690c2908ac15a1 Mon Sep 17 00:00:00 2001
From: Fabian Joswig <fabian.joswig@ed.ac.uk>
Date: Tue, 2 Nov 2021 11:09:43 +0000
Subject: [PATCH] Corr objects now support slicing, T_symmetry implemented for
 Corr objects

---
 pyerrors/correlators.py | 19 +++++++++++++++++++
 pyerrors/pyerrors.py    | 20 --------------------
 2 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/pyerrors/correlators.py b/pyerrors/correlators.py
index 1e182f31..a65a32e5 100644
--- a/pyerrors/correlators.py
+++ b/pyerrors/correlators.py
@@ -62,6 +62,9 @@ class Corr:
 
         self.gamma_method()
 
+    def __getitem__(self, idx):
+        return self.content[idx]
+
     def gamma_method(self):
         for item in self.content:
             if not(item is None):
@@ -206,6 +209,22 @@ class Corr:
     def reverse(self):
         return Corr(self.content[::-1])
 
+    def T_symmetry(partner, parity=+1):
+        if not isinstance(partner, Corr):
+            raise Exception("T partner has to be a Corr object.")
+        if parity not in [+1, -1]:
+            raise Exception("Parity has to be +1 or -1.")
+        T_partner = parity * partner.reverse()
+        t_slices = []
+        for x0, t_slice in enumerate(self - T_partner):
+            if t_slice is not None:
+                if not t_slice.is_zero_within_error(3):
+                    t_slices.append(x0)
+        if t_slices:
+            warnings.warn("T symmetry partner do not agree within 5 sigma on time slices" + str(t_slices) + ".", RuntimeWarning)
+
+        return (self + T_partner) / 2
+
     def deriv(self, symmetric=True):  # Defaults to symmetric derivative
         if not symmetric:
             newcontent = []
diff --git a/pyerrors/pyerrors.py b/pyerrors/pyerrors.py
index 8daac2bb..fc184f53 100644
--- a/pyerrors/pyerrors.py
+++ b/pyerrors/pyerrors.py
@@ -1405,26 +1405,6 @@ def covariance3(obs1, obs2, correlation=False, **kwargs):
     return cov
 
 
-def use_time_reversal_symmetry(data1, data2, **kwargs):
-    """Combine two correlation functions (lists of Obs) according to time reversal symmetry
-
-    Keyword arguments
-    -----------------
-    minus -- if True, multiply the second correlation function by a minus sign.
-    """
-    if kwargs.get('minus'):
-        sign = -1
-    else:
-        sign = 1
-
-    result = []
-    T = int(len(data1))
-    for i in range(T):
-        result.append(derived_observable(lambda x, **kwargs: (x[0] + sign * x[1]) / 2, [data1[i], data2[T - i - 1]], **kwargs))
-
-    return result
-
-
 def pseudo_Obs(value, dvalue, name, samples=1000):
     """Generate a pseudo Obs with given value, dvalue and name