Update comments and some __str__ methods

2 files changed, 8 insertions, 4 deletions

diff --git a/polymatrix/expression/impl.py b/polymatrix/expression/impl.py
index bbd932a..ac15aef 100644
--- a/polymatrix/expression/impl.py
+++ b/polymatrix/expression/impl.py
@@ -145,7 +145,7 @@ class DerivativeExprImpl(DerivativeExprMixin):
         return f"{self.__class__.__name__}(variables={self.variables}, underlying={repr(self.underlying)})"
 
     def __str__(self):
-        return f"∂_{self.variables} {self.underlying}"
+        return f"(∂_{self.variables} {self.underlying})"
 
 
 @dataclassabc.dataclassabc(frozen=True)
@@ -463,6 +463,9 @@ class SubtractMonomialsExprImpl(SubtractMonomialsExprMixin):
 class SumExprImpl(SumExprMixin):
     underlying: ExpressionBaseMixin
 
+    def __str__(self):
+        return f"(Σ {self.underlying})"
+
 
 @dataclassabc.dataclassabc(frozen=True)
 class SymmetricExprImpl(SymmetricExprMixin):
@@ -489,7 +492,7 @@ class TransposeExprImpl(TransposeExprMixin):
     underlying: ExpressionBaseMixin
 
     def __str__(self):
-        return f"({self.underlying}).T"
+        return f"{self.underlying}.T"
 
 
 @dataclassabc.dataclassabc(frozen=True)
diff --git a/polymatrix/polymatrix/mixins.py b/polymatrix/polymatrix/mixins.py
index f5cdb48..c12f4cc 100644
--- a/polymatrix/polymatrix/mixins.py
+++ b/polymatrix/polymatrix/mixins.py
@@ -460,7 +460,8 @@ class PolyMatrixAsAffineExpressionMixin(PolyMatrixMixin, ABC):
 
         else:
             # TODO: document behaviour on why it is allowed to pass varirables
-            # it has to do with sumofsquares/solver/cvxopt.py
+            # it has to do with the function
+            # sumofsquares.problems.InternalSOSProblem.to_conic_problem
             variables = tuple(sorted(variables))
 
         for degree in range(self.degree +1):
@@ -504,7 +505,7 @@ class PolyMatrixAsAffineExpressionMixin(PolyMatrixMixin, ABC):
         # efficiency gain is useless if most of the computed terms are not
         # used.
         # TODO: tune heuristic
-        if len(self.slices) > (n / 2):
+        if len(self.slices) > n:
             # Compute all powers of x up to degree d
             all_monomials = self.monomials_eval_all(x)
             monomials = {