From 8357464e3e1dd726cb0d1513d12f350c7cfd555b Mon Sep 17 00:00:00 2001
From: Frederik Hennig <frederik.hennig@fau.de>
Date: Mon, 18 Dec 2023 13:09:48 +0100
Subject: [PATCH] small fixes to dispatcher
---
src/pystencilssfg/visitors/dispatcher.py | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
diff --git a/src/pystencilssfg/visitors/dispatcher.py b/src/pystencilssfg/visitors/dispatcher.py
index 0b47534..f0bc005 100644
--- a/src/pystencilssfg/visitors/dispatcher.py
+++ b/src/pystencilssfg/visitors/dispatcher.py
@@ -6,7 +6,6 @@ from functools import wraps
V = TypeVar("V")
R = TypeVar("R")
-P = ParamSpec("P")
class VisitorDispatcher(Generic[V, R]):
@@ -15,7 +14,7 @@ class VisitorDispatcher(Generic[V, R]):
self._wrapped_method: Callable[..., R] = wrapped_method
def case(self, node_type: type):
- """Decorator for visitor's methods"""
+ """Decorator for visitor's case handlers."""
def decorate(handler: Callable[..., R]):
if node_type in self._dispatch_dict:
@@ -42,8 +41,8 @@ def visitor(method):
"""Decorator to create a visitor using type-based dispatch.
Use this decorator to convert a method into a visitor, like shown below.
- After declaring a method `<method-name>` a visitor,
- its dispatch variants can be declared using the `<method-name>,case` decarator, like this:
+ After declaring a method (e.g. `my_method`) a visitor,
+ its case handlers can be declared using the `my_method.case` decorator, like this:
```Python
class DemoVisitor:
@@ -57,15 +56,14 @@ def visitor(method):
# code for handling a str
```
- Now, if `visit` is called with an object of type `str`, the call is dispatched to `visit_str`.
- Dispatch follows the Python method resolution order; if cases are declared for both a type
- and some of its parent types, the most specific case is executed.
- If no case matches, the fallback code in the original `visit` method is executed.
+ When `visit` is later called with some object `x`, the case handler to be executed is
+ determined according to the method resolution order of `x` (i.e. along its type's inheritance hierarchy).
+ If no case matches, the fallback code in the original visitor method is executed.
+ In this example, if `visit` is called with an object of type `str`, the call is dispatched to `visit_str`.
This visitor dispatch method is primarily designed for traversing abstract syntax tree structures.
- The primary visitor method (`visit` in above example) defines the common parent type of all object
- types the visitor can handle - every case's type must be a subtype of this.
- Of course, like in the example, this visitor dispatcher may be used with arbitrary types if the base
- type is `object`.
+ The primary visitor method (`visit` in above example) should define the common parent type of all object
+ types the visitor can handle, with cases declared for all required subtypes.
+ However, this type relationship is not enforced at runtime.
"""
return wraps(method)(VisitorDispatcher(method))
--
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