From 0f4cd56b8539dfd986c9957a214de5d5d4795198 Mon Sep 17 00:00:00 2001
From: Thomas Haener <thomas_haener@hotmail.com>
Date: Wed, 31 Jan 2018 09:51:10 +0100
Subject: [PATCH] Added hash to DaggeredGate, including test.

---
 projectq/ops/_metagates.py      | 3 +++
 projectq/ops/_metagates_test.py | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/projectq/ops/_metagates.py b/projectq/ops/_metagates.py
index 684bcf9cb..3bcdae528 100755
--- a/projectq/ops/_metagates.py
+++ b/projectq/ops/_metagates.py
@@ -108,6 +108,9 @@ def __eq__(self, other):
         """
         return isinstance(other, self.__class__) and self._gate == other._gate
 
+    def __hash__(self):
+        return hash(str(self))
+
 
 def get_inverse(gate):
     """
diff --git a/projectq/ops/_metagates_test.py b/projectq/ops/_metagates_test.py
index 250499a9f..ea9526bcb 100755
--- a/projectq/ops/_metagates_test.py
+++ b/projectq/ops/_metagates_test.py
@@ -75,6 +75,15 @@ def test_daggered_gate_str():
     assert str(daggered_gate) == str(Y) + "^\dagger"
 
 
+def test_daggered_gate_hashable():
+    daggered_gate1 = _metagates.DaggeredGate(Y)
+    daggered_gate2 = _metagates.DaggeredGate(T)
+    d = {daggered_gate1 : 1, daggered_gate2 : 3}
+    assert len(d) == 2
+    # for efficiency reasons the following should be true:
+    assert hash(daggered_gate1) != hash(daggered_gate2)
+
+
 def test_daggered_gate_tex_str():
     daggered_gate = _metagates.DaggeredGate(Y)
     str_Y = Y.tex_str() if hasattr(Y, 'tex_str') else str(Y)