Bug/temp diff

src/ansys/units/quantity.py

@@ -1,4 +1,7 @@
+from typing import Tuple
+
 import ansys.units as q
+from ansys.units.units import parse_temperature_units
 
 
 class Quantity(float):
@@ -83,6 +86,11 @@ def __init__(self, value, units=None, quantity_map=None, dimensions=None):
         si_units, si_multiplier, si_offset = self._units_table.si_data(units=self._unit)
 
         self._si_units = si_units
+
+        # Well, this is going to have to be a hack, but we
+        # need to fix the wider design to do this properly
+        self._fix_temperature_units()
+
         self._si_value = (self.value + si_offset) * si_multiplier
 
     def _arithmetic_precheck(self, __value) -> str:
@@ -201,7 +209,7 @@ def __mul__(self, __value):
             ]
             new_si_value = self.si_value * __value.si_value
             new_dimensions = q.Dimensions(dimensions=temp_dimensions)
-            new_units = self._temp_precheck() or new_dimensions.units
+            new_units = new_dimensions.units
             return Quantity(value=new_si_value, units=new_units)
 
         if isinstance(__value, (float, int)):
@@ -218,15 +226,23 @@ def __truediv__(self, __value):
             ]
             new_si_value = self.si_value / __value.si_value
             new_dimensions = q.Dimensions(dimensions=temp_dimensions)
-            new_units = self._temp_precheck() or new_dimensions.units
-            return Quantity(value=new_si_value, units=new_units)
+            new_units = new_dimensions.units
+            result = Quantity(value=new_si_value, units=new_units)
+            # HACK
+            convert_to_temp_difference = (
+                "Temperature" == result.type
+                and __value.type in ("Temperature", "Temperature Difference")
+            )
+            if convert_to_temp_difference:
+                result._type = "Temperature Difference"
+            return result
 
         if isinstance(__value, (float, int)):
-            new_units = self._temp_precheck() or self.si_units
+            new_units = self.si_units
             return Quantity(value=self.si_value / __value, units=new_units)
 
     def __rtruediv__(self, __value):
-        return self.__truediv__(__value)
+        return Quantity(__value, "") / self
 
     def __add__(self, __value):
         self._arithmetic_precheck(__value)
@@ -273,6 +289,26 @@ def __neq__(self, __value):
         self._arithmetic_precheck(__value)
         return float(self) != float(__value)
 
+    @staticmethod
+    def _fix_these_temperature_units(
+        units: str, ignore_exponent: bool, units_to_search: Tuple[str] = None
+    ) -> str:
+        new_units = parse_temperature_units(units, ignore_exponent, units_to_search)
+        return " ".join(
+            ("delta_" + term[0])
+            if (term[1] and not term[0].startswith("delta_"))
+            else term[0]
+            for term in new_units
+        )
+
+    def _fix_temperature_units(self):
+        # HACK
+        ignore_exponent = self.type == "Temperature Difference"
+        self._unit = Quantity._fix_these_temperature_units(self._unit, ignore_exponent)
+        self._si_units = Quantity._fix_these_temperature_units(
+            self._si_units, ignore_exponent, ("K",)
+        )
+
 
 class QuantityError(ValueError):
     """Custom quantity errors."""

src/ansys/units/tables.py

@@ -3,6 +3,7 @@
 import yaml
 
 from ansys.units.quantity import Quantity, QuantityError  # noqa: F401
+from ansys.units.units import parse_temperature_units
 
 
 class UnitsTable(object):
@@ -293,7 +294,16 @@ def get_type(self, units: str) -> str:
         if units in self.derived_units:
             return "Derived"
 
-        if any([temp in units for temp in ["K", "C", "F", "R"]]):
-            return "Temperature Difference"
+        # HACK
+        temperature_units_to_search = ("K", "C", "F", "R")
+        if any([temp in units for temp in temperature_units_to_search]):
+            terms = parse_temperature_units(
+                units,
+                ignore_exponent=False,
+                units_to_search=temperature_units_to_search,
+            )
+            if any(is_diff for (_, is_diff) in terms):
+                return "Temperature Difference"
+            return "Temperature"
 
         return "Composite"

src/ansys/units/units.py

@@ -0,0 +1,20 @@
+from typing import Optional, Tuple
+
+
+def parse_temperature_units(
+    units: str, ignore_exponent: bool, units_to_search: Optional[Tuple[str]] = None
+) -> list:
+    if units_to_search is None:
+        units_to_search = ("K", "C", "F", "R")
+    units_out = []
+    for term in units.split(" "):
+        term_parts = term.split("^")
+        label = term_parts[0]
+        exponent = term_parts[0] if len(term_parts) > 1 else "0"
+        is_temp_diff = (
+            label
+            and (exponent != "0" or ignore_exponent)
+            and label[-1] in units_to_search
+        )
+        units_out.append((term, is_temp_diff))
+    return units_out

tests/test_quantity.py

@@ -254,14 +254,14 @@ def test_to_29():
     v = q.Quantity(1.0, "BTU lb^-1 R^-1")
     to = v.to("J kg^-1 K^-1")
     assert to.value == pytest.approx(4186.8161854, DELTA)
-    assert to.units == "J kg^-1 K^-1"
+    assert to.units == "J kg^-1 delta_K^-1"
 
 
 def test_to_30():
     v = q.Quantity(1.0, "BTU lb^-1 F^-1")
     to = v.to("J kg^-1 K^-1")
     assert to.value == pytest.approx(4186.8161854, DELTA)
-    assert to.units == "J kg^-1 K^-1"
+    assert to.units == "J kg^-1 delta_K^-1"
 
 
 def test_to_31():
@@ -537,37 +537,37 @@ def test_temp_7():
     hcto1 = hc.to("kJ kg^-1 K^-1")
 
     assert hcto1.value == pytest.approx(1.0, DELTA)
-    assert hcto1.units == "kJ kg^-1 K^-1"
+    assert hcto1.units == "kJ kg^-1 delta_K^-1"
 
     hcto2 = hc.to("J kg^-1 C^-1")
 
     assert hcto2.value == pytest.approx(1000.0, DELTA)
-    assert hcto2.units == "J kg^-1 C^-1"
+    assert hcto2.units == "J kg^-1 delta_C^-1"
 
     hcto3 = hc.to("kJ kg^-1 C^-1")
 
     assert hcto3.value == pytest.approx(1.0, DELTA)
-    assert hcto3.units == "kJ kg^-1 C^-1"
+    assert hcto3.units == "kJ kg^-1 delta_C^-1"
 
     hcto4 = hc.to("cal g^-1 C^-1")
 
     assert hcto4.value == pytest.approx(0.2390057, DELTA)
-    assert hcto4.units == "cal g^-1 C^-1"
+    assert hcto4.units == "cal g^-1 delta_C^-1"
 
     hcto5 = hc.to("cal kg^-1 C^-1")
 
     assert hcto5.value == pytest.approx(239.0057, DELTA)
-    assert hcto5.units == "cal kg^-1 C^-1"
+    assert hcto5.units == "cal kg^-1 delta_C^-1"
 
     hcto6 = hc.to("kcal kg^-1 C^-1")
 
     assert hcto6.value == pytest.approx(0.2390057, DELTA)
-    assert hcto6.units == "kcal kg^-1 C^-1"
+    assert hcto6.units == "kcal kg^-1 delta_C^-1"
 
     hcto7 = hc.to("BTU lb^-1 F^-1")
 
     assert hcto7.value == pytest.approx(0.238845, DELTA)
-    assert hcto7.units == "BTU lb^-1 F^-1"
+    assert hcto7.units == "BTU lb^-1 delta_F^-1"
 
 
 def test_temp_8():
@@ -576,32 +576,32 @@ def test_temp_8():
     temp_varto1 = temp_var.to("g cm^-3 s^-1 K^2")
 
     assert temp_varto1.value == pytest.approx(0.001, DELTA)
-    assert temp_varto1.units == "g cm^-3 s^-1 K^2"
+    assert temp_varto1.units == "g cm^-3 s^-1 delta_K^2"
 
     temp_varto2 = temp_var.to("kg mm^-3 s^-1 K^2")
 
     assert temp_varto2.value == pytest.approx(1e-09, DELTA)
-    assert temp_varto2.units == "kg mm^-3 s^-1 K^2"
+    assert temp_varto2.units == "kg mm^-3 s^-1 delta_K^2"
 
     temp_varto3 = temp_var.to("kg um^-3 s^-1 K^2")
 
     assert temp_varto3.value == pytest.approx(9.999999999999999e-19, DELTA)
-    assert temp_varto3.units == "kg um^-3 s^-1 K^2"
+    assert temp_varto3.units == "kg um^-3 s^-1 delta_K^2"
 
-    temp_varto4 = temp_var.to("mg mm^-3 ms^-1 K^2")
+    temp_varto4 = temp_var.to("mg mm^-3 ms^-1 delta_K^2")
 
     assert temp_varto4.value == pytest.approx(1.0000000000000002e-06, DELTA)
-    assert temp_varto4.units == "mg mm^-3 ms^-1 K^2"
+    assert temp_varto4.units == "mg mm^-3 ms^-1 delta_K^2"
 
     temp_varto5 = temp_var.to("g cm^-3 us^-1 K^2")
 
     assert temp_varto5.value == pytest.approx(1e-09, DELTA)
-    assert temp_varto5.units == "g cm^-3 us^-1 K^2"
+    assert temp_varto5.units == "g cm^-3 us^-1 delta_K^2"
 
     temp_varto6 = temp_var.to("pg um^-3 ms^-1 K^2")
 
     assert temp_varto6.value == pytest.approx(9.999999999999997e-07, DELTA)
-    assert temp_varto6.units == "pg um^-3 ms^-1 K^2"
+    assert temp_varto6.units == "pg um^-3 ms^-1 delta_K^2"
 
 
 def test_temp_inverse_1():
@@ -676,6 +676,36 @@ def test_temp_difference():
         t = tc1 + td1
 
 
+def test_temp_diff_combined_multiply():
+    k = q.Quantity(1.38e-23, "J K^-1")
+    t = q.Quantity(4.0, "K")
+    e = k * t
+    assert e.value == 5.52e-23
+    assert e.units == "kg m^2 s^-2"
+
+
+def test_temp_diff_combined_multiply_2():
+    q1 = q.Quantity(2.0, "J K^-2")
+    q2 = q.Quantity(4.0, "K")
+    res = q1 * q2
+    assert res.value == 8.0
+    assert res.units == "kg m^2 s^-2 delta_K^-1"
+
+
+def test_temp_diff_combined_inverse():
+    t = q.Quantity(4.0, "K")
+    inv_t = 2.0 / t
+    assert inv_t.value == 0.5
+    assert inv_t.units == "delta_K^-1"
+
+
+def test_temp_diff_combined_divide():
+    t = q.Quantity(4.0, "K")
+    t_div = t / 2.0
+    assert t_div.value == 2.0
+    assert t_div.units == "K"
+
+
 def test_core_temp():
     t1 = q.Quantity(1.0, "K")
     assert float(t1) == 1.0