Fix

nifty6/library/special_distributions.py

@@ -40,15 +40,17 @@ class _InterpolationOperator(Operator):
 
     def apply(self, x):
         self._check_input(x)
-        val = (np.clip(x.val, self._xmin, self._xmax) - self._xmin) / self._d
+        lin = isinstance(x, Linearization)
+        xval = x.val.val if lin else x.val
+        val = (np.clip(xval, self._xmin, self._xmax) - self._xmin) / self._d
         fi = np.floor(val).astype(int)
         w = val - fi
         res = self._inv_table_func((1-w)*self._table[fi] + w*self._table[fi+1])
         resfld = Field(self._domain, res)
-        if not isinstance(x, Linearization):
+        if not lin:
             return resfld
         jac = makeOp(Field(self._domain, self._deriv[fi]*res))
-        return Linearization(resfld, jac)
+        return x.new(resfld, jac)
 
 
 def InverseGammaOperator(domain, alpha, q, delta=0.001):