From 59cb6cf3273540fc2474c91555c273ebe8cc9b2e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Robert?= <cr52@protonmail.com>
Date: Sun, 2 Apr 2023 18:26:16 +0200
Subject: [PATCH 1/3] TST: add a broken test to expose bug #407

---
 unyt/tests/test_units.py | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/unyt/tests/test_units.py b/unyt/tests/test_units.py
index fd70b6d4..41322e6a 100644
--- a/unyt/tests/test_units.py
+++ b/unyt/tests/test_units.py
@@ -504,15 +504,25 @@ def test_base_equivalent():
     assert u.get_base_equivalent(unit_system="mks") == Unit("A")
 
 
-def test_temperature_offsets():
-    u1 = Unit("degC")
-    u2 = Unit("degF")
-
+@pytest.mark.parametrize(
+    ("u1", "u2"),
+    [
+        (Unit("degC"), Unit("degF")),
+        (Unit("degC"), Unit("K")),
+        (Unit("degF"), Unit("K")),
+    ],
+)
+def test_temperature_offsets(u1, u2):
     with pytest.raises(InvalidUnitOperation):
         operator.mul(u1, u2)
     with pytest.raises(InvalidUnitOperation):
         operator.truediv(u1, u2)
 
+    assert u1 != u2
+    assert u2 != u1
+    assert not u1 == u2
+    assert not u2 == u1
+
 
 def test_latex_repr():
     registry = UnitRegistry()

From d66608affc2140d77b17ce619080625c8dc9a2b7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Robert?= <cr52@protonmail.com>
Date: Sun, 2 Apr 2023 18:33:45 +0200
Subject: [PATCH 2/3] BUG: fix unit comparison for K VS degC

---
 unyt/array.py       |  6 +++++-
 unyt/unit_object.py | 25 +++++++++----------------
 2 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/unyt/array.py b/unyt/array.py
index efc0f3da..34db5774 100644
--- a/unyt/array.py
+++ b/unyt/array.py
@@ -1884,7 +1884,11 @@ def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
                     conv, offset = u1.get_conversion_factor(u0, inp1.dtype)
                     new_dtype = np.dtype("f" + str(inp1.dtype.itemsize))
                     conv = new_dtype.type(conv)
-                    if offset is not None:
+                    if (
+                        offset is not None
+                        and u1.base_offset != 0.0
+                        and not repr(u0).startswith("delta_")
+                    ):
                         raise InvalidUnitOperation(
                             "Quantities with units of Fahrenheit or Celsius "
                             "cannot by multiplied, divided, subtracted or "
diff --git a/unyt/unit_object.py b/unyt/unit_object.py
index 2b13e46d..5b734ef2 100644
--- a/unyt/unit_object.py
+++ b/unyt/unit_object.py
@@ -480,25 +480,18 @@ def __pow__(self, p):
 
     def __eq__(self, u):
         """Test unit equality."""
-        if not isinstance(u, Unit):
-            return False
         return (
-            math.isclose(self.base_value, u.base_value)
-            and self.dimensions == u.dimensions
+            isinstance(u, Unit)
+            and math.isclose(self.base_value, u.base_value)
+            and math.isclose(self.base_offset, u.base_offset)
+            and (
+                # use 'is' comparison dimensions to avoid expensive sympy operation
+                self.dimensions is u.dimensions
+                # fall back to expensive sympy comparison
+                or self.dimensions == u.dimensions
+            )
         )
 
-    def __ne__(self, u):
-        """Test unit inequality."""
-        if not isinstance(u, Unit):
-            return True
-        if not math.isclose(self.base_value, u.base_value):
-            return True
-        # use 'is' comparison dimensions to avoid expensive sympy operation
-        if self.dimensions is u.dimensions:
-            return False
-        # fall back to expensive sympy comparison
-        return self.dimensions != u.dimensions
-
     def copy(self, *, deep=False):
         expr = str(self.expr)
         base_value = copy.deepcopy(self.base_value)

From d0a4017ba8ebdfa54a84f13445e8d48d4a4d6d11 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Robert?= <cr52@protonmail.com>
Date: Sat, 8 Apr 2023 19:05:19 +0200
Subject: [PATCH 3/3] DOC: fixup doctest (temperature sums and differences are
 now float typed)

---
 docs/usage.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/usage.rst b/docs/usage.rst
index 35644609..cc4a097d 100644
--- a/docs/usage.rst
+++ b/docs/usage.rst
@@ -363,9 +363,9 @@ Performing arithmetic with temperature quantities can be ambiguous. To clarify i
   >>> t1 = 23*degC
   >>> t2 = 1*delta_degC
   >>> print(t1 + t2)
-  24 °C
+  24.0 °C
   >>> print(t2 - t1)
-  -22 °C
+  -22.0 °C
   >>> tempco = 10.0*V/delta_degC
   >>> print(tempco*2*delta_degC)
   20.0 V