Add () around 0-degree coefficient if it has a + separator

Fixes #328

galois/_poly_conversion.py

@@ -98,7 +98,6 @@ def sparse_poly_to_str(degrees: List[int], coeffs: List[int], poly_var: str = "x
  if coeff == 0:
  continue
 
- # Use () around elements, except the 0-th degree term
  if degree > 1:
  if coeff == 1:
  c = ""
@@ -116,7 +115,11 @@ def sparse_poly_to_str(degrees: List[int], coeffs: List[int], poly_var: str = "x
  c = f"{coeff!s}"
  s = f"{c}{poly_var}"
  else:
- s = f"{coeff!s}"
+ # Use () around 0-degree term only if it has a + separator in it ("poly" display mode)
+ if "+" in str(coeff):
+ s = f"({coeff!s})"
+ else:
+ s = f"{coeff!s}"
 
  x.append(s)
 

tests/polys/test_conversions.py

@@ -61,10 +61,10 @@ def test_sparse_poly_to_str():
  GF = galois.GF(2**8)
  with GF.display("poly"):
  assert galois._poly_conversion.sparse_poly_to_str([0], GF([0])) == "0"
- assert galois._poly_conversion.sparse_poly_to_str([3, 1, 0], GF([1, 2, 3])) == "x^3 + (α)x + α + 1"
+ assert galois._poly_conversion.sparse_poly_to_str([3, 1, 0], GF([1, 2, 3])) == "x^3 + (α)x + (α + 1)"
 
  assert galois._poly_conversion.sparse_poly_to_str([0], GF([0]), poly_var="y") == "0"
- assert galois._poly_conversion.sparse_poly_to_str([3, 1, 0], GF([1, 2, 3]), poly_var="y") == "y^3 + (α)y + α + 1"
+ assert galois._poly_conversion.sparse_poly_to_str([3, 1, 0], GF([1, 2, 3]), poly_var="y") == "y^3 + (α)y + (α + 1)"
 
 
 def test_str_to_sparse_poly():

tests/polys/test_operations.py

@@ -106,12 +106,12 @@ def test_str():
  assert str(poly) == "(α^5)x^3 + (α)x + 1"
 
  GF = galois.GF(2**3)
- poly = galois.Poly([2, 0, 3, 1], field=GF)
- assert str(poly) == "2x^3 + 3x + 1"
+ poly = galois.Poly([2, 0, 3, 5], field=GF)
+ assert str(poly) == "2x^3 + 3x + 5"
  with GF.display("poly"):
- assert str(poly) == "(α)x^3 + (α + 1)x + 1"
+ assert str(poly) == "(α)x^3 + (α + 1)x + (α^2 + 1)"
  with GF.display("power"):
- assert str(poly) == "(α)x^3 + (α^3)x + 1"
+ assert str(poly) == "(α)x^3 + (α^3)x + α^6"
 
 
 def test_int():