Fixed #44, added syntax for selecting blades of a given grade.

kingdon/algebra.py

@@ -479,3 +479,15 @@ def __len__(self):
 
     def __iter__(self):
         return iter(self.blades)
+
+    def grade(self, *grades) -> dict:
+        """
+        Return blades of grade `grades`.
+
+        :param grades: tuple or ints, grades to select.
+        """
+        if len(grades) == 1 and isinstance(grades[0], tuple):
+            grades = grades[0]
+
+        return {(blade := self.algebra.bin2canon[k]): self[blade]
+                for k in self.algebra.indices_for_grades[grades]}

tests/test_kingdon.py

@@ -821,3 +821,11 @@ def test_43():
     alg = Algebra(2)
     x = alg.vector(name='x')
     assert x.inv() == 1 / x
+
+def test_blades_of_grade():
+    alg = Algebra(4)
+    for indices in alg.indices_for_grades:
+        blades_of_grade = alg.blades.grade(*indices)
+        assert isinstance(blades_of_grade, dict)
+        assert all(label in alg.canon2bin and blade.grades[0] in indices
+                   for label, blade in blades_of_grade.items())