Piecewise utility function feature

configs/round_configs/demo.yaml

@@ -23,7 +23,12 @@ trade_box_scale: 0.2
 # this calculation is done after scaling, so x and y are fractional values
 # this function needs to be both valid javascript and python code which means available operations are
 # pretty much just limited to arithmetic
-utility_function: "(x ** 0.5) * (y ** 0.5)"
+
+# if the parameter 'piecewise_utility' is True, the syntax should be a string like this one
+#"(piece 1, domain for piece 1);(piece 2, domain for piece 2)...". e.g: “(11 + 12*(x+(11.2*y - 0.5*(y**2))), y<11.2);(11 + 12*(x + 0.5*(11.2**2)), y>=11.2)”
+# else, the syntax is a string with the "function". e.g: "(x ** 0.5) * (y ** 0.5)"
+piecewise_utility: true
+utility_function: “(11 + 12*(x+(11.2*y - 0.5*(y**2))), y<11.2);(11 + 12*(x + 0.5*(11.2**2)), y>=11.2)”
 # the maximum utility value which can be reached by a player
 # this is used to scale displayed utility values when generating the heatmap
 max_utility: 50

models.py

@@ -135,7 +135,27 @@ def config(self):
         return MarketConfig.get(config_name, self.round_number, self.id_in_group)
 
     def utility_function(self, x, y):
-        return eval(self.config.utility_function, {'x': x, 'y': y})
+        """
+        Evaluates the inputted parameters on a continuous/piecewise function
+
+        Input: parameter values for x and y (float)
+        Output: value of function after evaluating the values (float)
+        """
+
+        if not self.config.piecewise_utility:
+            return eval(self.config.utility_function, {'x': x, 'y': y})
+        else:
+            pieces = self.config.utility_function.split(";")
+
+            for piece in pieces: # iterating through pieces of function
+                # extracting value under current piece and condition
+                value_and_cond = eval(piece, {'x': x, 'y': y})
+                piece_value = value_and_cond[0] 
+                condition_is_met = value_and_cond[1] 
+
+                if condition_is_met:
+                    return piece_value
+
 
     def set_payoff(self):
         config = self.config