fix l_poly compatibility with rv_frozen

lmo/distributions.py

@@ -861,15 +861,28 @@ def l_kurtosis(self, trim: AnyTrim | None = None) -> float:
         """
         return float(self.l_ratio(4, 2, trim=trim))
 
+    # `rv_continuous` and `rv_frozen` compatibility
+
+    @property
+    def dist(self) -> type[Self]:  # noqa: D102
+        return type(self)
+
+    @property
+    def args(self) -> _LPolyParams:  # noqa: D102
+        return (self._l_moments, self._trim)
+
+    @property
+    def kwds(self) -> dict[str, Any]:  # noqa: D102
+        return {}
+
     @classmethod
-    def freeze(
+    def freeze(  # noqa: D102
         cls,
         lmbda: lnpt.AnyVectorFloat,
         /,
         trim: AnyTrim = 0,
         **kwds: Any,
     ) -> Self:
-        """For compatibility with `rv_generic`."""
         return cls(lmbda, trim, **kwds)
 
     @overload

lmo/typing/_scipy.py

@@ -340,6 +340,29 @@ def nnlf(
 
 @runtime_checkable
 class RVDiscrete(RV, Protocol):
+    """
+    Runtime-checkable interface for discrete probability distributions,
+    like [`scipy.stats.rv_discrete`][scipy.stats.rv_discrete] subtype
+    instances.
+
+    Examples:
+        >>> import numpy as np
+        >>> from scipy.stats import distributions as distrs
+        >>> isinstance(distrs.binom, RVDiscrete)
+        True
+
+        Continuous distributions aren't included:
+
+        >>> isinstance(distrs.norm, RVDiscrete)
+        False
+
+        Note that for "frozen" distributions (a.k.a. random variables),
+        this is not the case:
+
+        >>> isinstance(distrs.binom(5, .42), RVDiscrete)
+        False
+    """
+
     @property
     def inc(self) -> int: ...
 
@@ -741,6 +764,21 @@ def expect(
 
 @runtime_checkable
 class RVDiscreteFrozen(RVFrozen[_RV_D_co], Protocol[_RV_D_co]):
+    """
+    Runtime-checkable interface for discrete probability distributions,
+    like [`scipy.stats.rv_discrete`][scipy.stats.rv_discrete] subtype
+    instances.
+
+    Examples:
+        >>> import numpy as np
+        >>> from scipy.stats import distributions as distrs
+        >>> isinstance(distrs.bernoulli, RVDiscreteFrozen)
+        False
+        >>> isinstance(distrs.bernoulli(.42), RVDiscreteFrozen)
+        True
+        >>> isinstance(distrs.uniform(), RVDiscreteFrozen)
+        False
+    """
     @overload
     def pmf(self, k: _Real0D) -> _F8: ...
     @overload
@@ -760,6 +798,28 @@ def logpmf(self, k: lnpt.AnyArrayFloat) -> lnpt.Array[_ND1, _F8]: ...
 
 @runtime_checkable
 class RVContinuousFrozen(RVFrozen[_RV_C_co], Protocol[_RV_C_co]):
+    """
+    Runtime-checkable interface for discrete probability distributions,
+    like [`scipy.stats.rv_discrete`][scipy.stats.rv_discrete] subtype
+    instances.
+
+    Examples:
+        >>> import numpy as np
+        >>> from scipy.stats import distributions as distrs
+        >>> isinstance(distrs.uniform, RVContinuousFrozen)
+        False
+        >>> isinstance(distrs.uniform(), RVContinuousFrozen)
+        True
+        >>> isinstance(distrs.bernoulli(.5), RVContinuousFrozen)
+        False
+
+        >>> from lmo.distributions import l_poly
+        >>> isinstance(l_poly([0, 1/6]), RVContinuousFrozen)
+        True
+        >>> isinstance(l_poly, RVContinuousFrozen)
+        True
+    """
+
     @overload
     def pdf(self, x: _Real0D) -> _F8: ...
     @overload