some cleanups/ interval error checking

Project/Assets/ML-Agents/Examples/3DBall/Scripts/Ball3DAgent.cs

     public void SetBall()
     {
         //Set the attributes of the ball by fetching the information from the academy
-        //m_BallRb.mass = m_ResetParams.GetWithDefault("mass", 1.0f);
-        m_BallRb.mass = m_ResetParams.Sample("mass", 1.0f);
-        var scale = m_ResetParams.Sample("scale", 1.0f);
+        m_BallRb.mass = m_ResetParams.GetWithDefault("mass", 1.0f);
+        var scale = m_ResetParams.GetWithDefault("scale", 1.0f);
         ball.transform.localScale = new Vector3(scale, scale, scale);
     }
 

com.unity.ml-agents/Runtime/EnvironmentParameters.cs

             return m_Channel.GetWithDefault(key, defaultValue);
         }
 
-        public float Sample(string key, float defaultValue)
-        {
-            return m_Channel.Sample(key, defaultValue);
-        }
-
         /// <summary>
         /// Registers a callback action for the provided parameter key. Will overwrite any
         /// existing action for that parameter. The callback will be called whenever the parameter

com.unity.ml-agents/Runtime/SideChannels/EnvironmentParametersChannel.cs

     /// </summary>
     internal class EnvironmentParametersChannel : SideChannel
     {
-        Dictionary<string, float> m_Parameters = new Dictionary<string, float>();
-        Dictionary<string, Func<float>> m_Samplers = new Dictionary<string, Func<float>>();
+        Dictionary<string, Func<float>> m_Parameters = new Dictionary<string, Func<float>>();
         Dictionary<string, Action<float>> m_RegisteredActions =
             new Dictionary<string, Action<float>>();
 
             {
                 var value = msg.ReadFloat32();
 
-                m_Parameters[key] = value;
+                m_Parameters[key] = () => value;
 
                 Action<float> action;
                 m_RegisteredActions.TryGetValue(key, out action);
             {
                 var encoding = msg.ReadFloatList(); 
-                m_Samplers[key] = m_SamplerFactory.CreateSampler(encoding);
-                //var samplerType = msg.ReadFloat32();
-                //var statOne = msg.ReadFloat32();
-                //var statTwo = msg.ReadFloat32();
-                //m_Parameters[key+"-sampler-type"] = samplerType;
-                //m_Parameters[key+"-min"] = statOne;
-                //m_Parameters[key+"-max"] = statTwo;
+                m_Parameters[key] = m_SamplerFactory.CreateSampler(encoding);
             }
             else
             {
         /// <returns></returns>
         public float GetWithDefault(string key, float defaultValue)
         {
-            float valueOut;
-            bool hasKey = m_Parameters.TryGetValue(key, out valueOut);
-            return hasKey ? valueOut : defaultValue;
-        }
-
-        public float Sample(string key, float defaultValue)
-        {
-            bool hasKey = m_Samplers.TryGetValue(key, out valueOut);
+            bool hasKey = m_Parameters.TryGetValue(key, out valueOut);
-
-        /// <summary>
-        /// Returns the parameter value associated with the provided key. Returns the default
-        /// value if one doesn't exist.
-        /// </summary>
-        /// <param name="key">Parameter key.</param>
-        /// <param name="defaultValue">Default value to return.</param>
-        /// <returns></returns>
-        public float GetListWithDefault(string key, float defaultValue)
-        {
-            float valueOut;
-            bool hasKey = m_Parameters.TryGetValue(key, out valueOut);
-            return hasKey ? valueOut : defaultValue;
-        }
-
+        
         /// <summary>
         /// Registers a callback for the associated parameter key. Will overwrite any existing
         /// actions for this parameter key.

ml-agents-envs/mlagents_envs/side_channel/environment_parameters_channel.py

 
     def set_sampler_parameters(self, key: str, values: List[float]) -> None:
         """
-        Sets a float environment parameter in the Unity Environment.
+        Sets a float encoding of an environment parameter sampelr.
-        :param value: The float value of the parameter.
+        :param value: The float encoding  of the sampler.
         """
         msg = OutgoingMessage()
         msg.write_string(key)

ml-agents/mlagents/trainers/settings.py

     max_value: float = 1.0
 
     def to_float(self) -> List[float]:
+        if self.min_value > self.max_value:
+            raise TrainerConfigError(
+                "Minimum value is greater than maximum value in uniform sampler."
+            )
         return [0.0, self.min_value, self.max_value]
 
 
     intervals: List[List[float]] = [[1.0, 1.0]]
 
     def to_float(self) -> List[float]:
-        return [2.0] + [val for interval in self.intervals for val in interval]
+        floats: List[float] = []
+        for interval in self.intervals:
+            if len(interval) != 2:
+                raise TrainerConfigError(
+                    f"The sampling interval {interval} must contain exactly two values."
+                )
+            [min_value, max_value] = interval
+            if min_value > max_value:
+                raise TrainerConfigError(
+                    f"Minimum value is greater than maximum value in interval {interval}."
+                )
+            floats += interval
+        return [2.0] + floats
 
 
 @attr.s(auto_attribs=True)