Accept polynomial coefficient lists in RationalFunction2

blueprint/src/python/functions.py

@@ -672,7 +672,7 @@ def __init__(self, coeffs, domain):
         if len(coeffs) == 0:
             raise ValueError("Parameter coeffs must have at least 1 element")
 
-        if len(coeffs) == 1:
+        if isinstance(coeffs, list) or len(coeffs) == 1:
             self._num_coeffs = tuple(coeffs)
             self._den_coeffs = tuple([1])
         else:

blueprint/src/python/tests/test_polynomial_input_regression.py

@@ -0,0 +1,20 @@
+from functions import Interval, RationalFunction2
+
+
+def test_multi_coefficient_polynomial_input():
+    function = RationalFunction2([1, 2, 3], Interval(0, 1))
+    assert function._num_coeffs == (1, 2, 3)
+    assert function._den_coeffs == (1,)
+    assert str(function) == "x^2 + 2x + 3 on [0,1)"
+
+
+def test_rational_pair_input_unchanged():
+    function = RationalFunction2(([1, 2], [3, 4]), Interval(0, 1))
+    assert function._num_coeffs == (1, 2)
+    assert function._den_coeffs == (3, 4)
+
+
+def test_single_coefficient_input_unchanged():
+    function = RationalFunction2([2], Interval(0, 1))
+    assert function._num_coeffs == (2,)
+    assert function._den_coeffs == (1,)