Implement Constant logcdf

Author: ricardoV94

pymc/distributions/discrete.py

@@ -1378,6 +1378,13 @@ def logp(value, c):
             -np.inf,
         )
 
+    def logcdf(value, c):
+        return at.switch(
+            at.lt(value, c),
+            -np.inf,
+            0,
+        )
+
 
 class ZeroInflatedPoissonRV(RandomVariable):
     name = "zero_inflated_poisson"

pymc/tests/test_distributions.py

@@ -1744,6 +1744,7 @@ def test_poisson(self):
 
     def test_constantdist(self):
         self.check_logp(Constant, I, {"c": I}, lambda value, c: np.log(c == value))
+        self.check_logcdf(Constant, I, {"c": I}, lambda value, c: np.log(value >= c))
 
     def test_zeroinflatedpoisson(self):
         def logp_fn(value, psi, theta):