fix #4 - error calling pdf in discrete_mdp

Author: tawheeler

src/DecisionMakingProblems.jl

@@ -9,7 +9,7 @@ using Parameters
 using Statistics
 using Printf
 
-export 
+export
     MDP, HexWorld, StraightLineHexWorld, TwentyFortyEight, CartPole, MountainCar, LQR, CollisionAvoidance,
     POMDP, DiscretePOMDP, CryingBaby, MachineReplacement, Catch,
     SimpleGame, PrisonersDilemma, RockPaperScissors, Travelers,
@@ -18,6 +18,7 @@ export
     DecPOMDP, CollaborativePredatorPreyHexWorld, SimpleCollaborativePredatorPreyHexWorld, CircleCollaborativePredatorPreyHexWorld
 
 import Base: <, ==, rand, vec
+import Distributions: pdf
 
 include("support_code.jl")
 

src/support_code.jl

@@ -25,6 +25,6 @@ end
 
 Distributions.rand(D::SetCategorical) = D.elements[rand(D.distr)]
 Distributions.rand(D::SetCategorical, n::Int) = D.elements[rand(D.distr, n)]
-function Distributions.pdf(D::SetCategorical, x)
+function pdf(D::SetCategorical, x)
     sum(e == x ? w : 0.0 for (e,w) in zip(D.elements, D.distr.p))
 end