added polar_str method

pyzx/graph/scalar.py

@@ -79,6 +79,14 @@ def __str__(self) -> str:
     def __complex__(self) -> complex:
         return self.to_number()
 
+    def polar_str(self) -> str:
+        """Returns a human-readable string of the scalar in polar format"""
+        r,th = cmath.polar(self.to_number())
+        s = "{:.3}".format(r)
+        if th != 0:
+            s += " * exp(i pi * {:.3})".format(th/math.pi)
+        return s
+
     def copy(self, conjugate: bool = False) -> 'Scalar':
         """Create a copy of the Scalar. If ``conjugate`` is set, the copy will be complex conjugated.
 
@@ -211,6 +219,8 @@ def add_node(self, node: FractionLike) -> None:
             self.phasenodes.append(node)
         if node == 1: self.is_zero = True
     def add_float(self,f: complex) -> None:
+        if f == 0.0:
+            self.is_zero = True
         self.floatfactor *= f
 
     def mult_with_scalar(self, other: 'Scalar') -> None:
@@ -260,4 +270,4 @@ def add_spider_pair(self, p1: FractionLike,p2: FractionLike) -> None:
         # Generic case
         self.add_power(-1)
         self.add_float(1+cexp(p1)+cexp(p2) - cexp(p1+p2))
-        return
+        return