Implement advance_generation

-Implement printing

src/population.py

@@ -7,10 +7,19 @@ rand = Random()
 class Population(object):
 
     def __init__(self, size):
-        self.members = []
+        self.members = list()
         for current in range(0, size):
             self.members.append(Individual())
 
+    def __str__(self):
+        return_string = ""
+        position = 0
+        for member in self.members:
+            return_string += "%d:\tx: %f\ty: %f\tfit: %f\n" %\
+                             (position, member.x, member.y, member.fitness)
+            position += 1
+        return return_string
+
     def fitness_function(self):
         for member in self.members:
             member.fitness_function()
@@ -24,11 +33,21 @@ class Population(object):
     def roulette(self, divisor=1):
         total = self.total_fitness() / divisor
         position = rand.uniform(0, total)
+
         for member in self.members:
             position -= member.fitness / divisor
             if position <= 0:
                 return member
 
     def advance_generation(self):
-        crossover_members = []
-        crossover_members.append(self.roulette())
+        self.fitness_function()
+        parents = list()
+        for i in range(0, len(self.members)):
+            parents.append(self.roulette())
+
+        children = list()
+        for i in range(0, len(parents) - 2, 2):
+            parents[i].crossover(parents[i + 1])
+            children.append(parents[i])
+            children.append(parents[i+1])
+        self.members = children