Hotfixes for WeightedParticles (#64)

* pass frozen when condense

* bug fix: cannot access private _hist of other

pomdp_py/representations/distribution/particles.pyx

@@ -53,6 +53,14 @@ cdef class WeightedParticles(GenerativeDistribution):
     def frozen(self):
         return self._frozen
 
+    @property
+    def hist(self):
+        return self._hist
+
+    @property
+    def hist_valid(self):
+        return self._hist_valid
+
     def add(self, particle):
         """add(self, particle)
         particle: (value, weight) tuple"""
@@ -77,7 +85,7 @@ cdef class WeightedParticles(GenerativeDistribution):
 
     def __eq__(self, other):
         if isinstance(other, WeightedParticles):
-            return self._hist == other._hist
+            return self._hist == other.hist
         return False
 
     def __getitem__(self, value):
@@ -161,7 +169,7 @@ cdef class WeightedParticles(GenerativeDistribution):
         Returns a new set of weighted particles with unique values
         and weights aggregated (taken average).
         """
-        return WeightedParticles.from_histogram(self.get_histogram())
+        return WeightedParticles.from_histogram(self.get_histogram(), frozen=self._frozen)
 
 
 cdef class Particles(WeightedParticles):