Add decimal number (bitmask), from Goyette (2012)

setclass/setclass.py

@@ -82,6 +82,16 @@ class SetClass(list):
         """Returns the brightness of the set class, defined as the sum of the pitch class values."""
         return sum(self.pitch_classes)
 
+    @cache_property
+    def decimal(self) -> int:
+        """
+        Returns the decimal value of the pitch classes expressed as a binary bit mask, i.e. the sum
+        of 2ⁱ where i is each pitch class value. For example, {0,1,4,6} has a binary value of
+        000001010011, which is the decimal value 83.
+        — Goyette (2012) p. 25, citing Brinkman (1986).
+        """
+        return sum([2**i for i in self.pitch_classes])
+
     @cache_property
     def adjacency_intervals(self) -> list(int):
         """Adjacency intervals between the pitch classes, used for Leonard notation subscripts."""

setclass/tests/test_setclass.py

@@ -86,6 +86,11 @@ def test_brightness():
     assert f520.brightness == 20
 
 
+def test_decimal():
+    "Set classes have a unique decimal number (sum of 2 raised to each normalised pitch class value)"
+    assert f520.decimal == 355
+
+
 def test_pitch_classes():
     "Set classes have pitch classes"
     assert len(f520) == 5
@@ -153,6 +158,10 @@ def test_complement_brightness():
     assert f520.complement.brightness == 32
 
 
+def test_complement_decimal():
+    assert f520.complement.decimal == 935
+
+
 def test_complement_pitch_classes():
     assert len(f520.complement) == 7
     assert len(f520.complement.pitch_classes) == 7