Add comparison for formulas.

2 files changed, 14 insertions, 2 deletions

diff --git a/pyecsca/ec/formula/base.py b/pyecsca/ec/formula/base.py
index 5cfb425..4b8d27d 100644
--- a/pyecsca/ec/formula/base.py
+++ b/pyecsca/ec/formula/base.py
@@ -276,6 +276,15 @@ class Formula(ABC):
                 result.append(point)
             return action.exit(tuple(result))
 
+    def __lt__(self, other):
+        if not isinstance(other, Formula):
+            raise TypeError("Cannot compare.")
+        if self.name is None:
+            return True
+        if other.name is None:
+            return False
+        return self.name < other.name
+
     def __str__(self):
         return f"{self.shortname}[{self.name}]"
 
diff --git a/test/ec/test_formula.py b/test/ec/test_formula.py
index a2af47e..42835a9 100644
--- a/test/ec/test_formula.py
+++ b/test/ec/test_formula.py
@@ -31,7 +31,6 @@ from pyecsca.ec.formula.efd import (
     AdditionEFDFormula,
     DoublingEFDFormula,
     LadderEFDFormula,
-    EFDFormula,
 )
 from pyecsca.ec.formula import (
     AdditionFormula,
@@ -149,6 +148,10 @@ def test_pickle(add, dbl):
     assert add == pickle.loads(pickle.dumps(add))
 
 
+def test_compare(add, dbl):
+    assert add < dbl
+
+
 def test_formula_similarity(secp128r1):
     add_bl = secp128r1.curve.coordinate_model.formulas["add-2007-bl"]
     add_rcb = secp128r1.curve.coordinate_model.formulas["add-2015-rcb"]
@@ -522,5 +525,5 @@ def test_formula_correctness(library_formula_params):
 
 
 def test_formula_expand(add):
-    res = expand_formula_set([add])
+    res = expand_formula_set({add})
     assert len(res) > 1