+Operator Standard binding Expected type
+--------------------------------------------------------------------
+return GHC.Base t1 -> m t2
+(>>=) GHC.Base m1 t1 -> (t2 -> m2 t3) -> m3 t3
+(>>) GHC.Base m1 t1 -> m2 t2 -> m3 t3
+guard Control.Monad t1 -> m t2
+fmap GHC.Base forall a b. (a->b) -> n a -> n b
+mgroupWith Control.Monad.Group forall a. (a -> t) -> m1 a -> m2 (n a)
+mzip Control.Monad.Zip forall a b. m a -> m b -> m (a,b)
+</programlisting>
+The comprehension should typecheck when its desugaring would typecheck.
+</para>
+<para>
+Monad comprehensions support rebindable syntax (<xref linkend="rebindable-syntax"/>).
+Without rebindable
+syntax, the operators from the "standard binding" module are used; with
+rebindable syntax, the operators are looked up in the current lexical scope.
+For example, parallel comprehensions will be typechecked and desugared
+using whatever "<literal>mzip</literal>" is in scope.
+</para>
+<para>
+The rebindable operators must have the "Expected type" given in the
+table above. These types are surprisingly general. For example, you can
+use a bind operator with the type
+<programlisting>
+(>>=) :: T x y a -> (a -> T y z b) -> T x z b
+</programlisting>
+In the case of transform comprehensions, notice that the groups are
+parameterised over some arbitrary type <literal>n</literal> (provided it
+has an <literal>fmap</literal>, as well as
+the comprehension being over an arbitrary monad.
+</para>