Document overload alternatives.

Refs #119.

README.md

@@ -100,16 +100,26 @@ for subclass in (float, list, list[float], tuple[int]):
     assert not issubclass(subclass, cls)
 ```
 
-If a type implements a custom `__instancecheck__`, it can opt-in to dispatch (without caching) by registering its metaclass and bases with `subtype.origins`. `parametric` provides a convenient constructor, with support for predicate functions and checking attributes.
+If a type implements a custom `__instancecheck__`, it can opt-in to dispatch (without caching) by registering its metaclass and bases with `subtype.origins`. `parametric` provides a convenient constructor, which will match the base class, predicate functions, and check attributes.
 
 ```python
 from multimethod import parametric
 
-coro = parametric(Callable, asyncio.iscoroutinefunction)
-ints = parametric(array, typecode='i')
+Coroutine = parametric(Callable, asyncio.iscoroutinefunction)
+IntArray = parametric(array, typecode='i')
 ```
 
-`overload` used to dispatch on annotated predicate functions. It is deprecated because a custom instance check - including using `parametric` - offers the same functionality.
+`overload` used to dispatch on annotated predicate functions. It is deprecated because a custom instance check - including using `parametric` - offers the same functionality. Any predicate function can be wrapped with the closest matching base class, including  `object` if necessary.
+
+```python
+Cls = parametric(object, predicate)
+Digits = parametric(str, str.isdigit)
+assert isinstance('0', Digits)
+assert not isinstance('a', Digits)
+
+@meth.register
+def _(arg: Digits): ...
+```
 
 ### classes
 `classmethod` and `staticmethod` may be used with a multimethod, but must be applied _last_, i.e., wrapping the final multimethod definition after all functions are registered. For class and instance methods, `cls` and `self` participate in the dispatch as usual. They may be left blank when using annotations, otherwise use `object` as a placeholder.

docs/examples.ipynb

@@ -133,7 +133,7 @@
    "metadata": {},
    "source": [
     "## parametric\n",
-    "In addition to `issubclass`, multimethods can dispatch on `isinstance` with additional parametric checks."
+    "In addition to `issubclass`, multimethods can dispatch on `isinstance` with parametric checks."
    ]
   },
   {
@@ -148,7 +148,7 @@
     "from concurrent import futures\n",
     "from multimethod import parametric\n",
     "\n",
-    "coro = parametric(Callable, asyncio.iscoroutinefunction)\n",
+    "Coroutine = parametric(Callable, asyncio.iscoroutinefunction)\n",
     "\n",
     "\n",
     "@multimethod\n",
@@ -157,7 +157,7 @@
     "\n",
     "\n",
     "@multimethod\n",
-    "async def wait(timeout, func: coro, *args):\n",
+    "async def wait(timeout, func: Coroutine, *args):\n",
     "    return await asyncio.wait_for(func(*args), timeout)\n",
     "\n",
     "\n",
@@ -173,6 +173,27 @@
     "wait(0.5, asyncio.sleep, 0.01)"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from array import array\n",
+    "\n",
+    "IntArray = parametric(array, typecode='i')\n",
+    "isinstance(array('i'), IntArray)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "isinstance(array('f'), IntArray)"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},