From 03937e62e61d7da1f3d41a3f58c3def033391be4 Mon Sep 17 00:00:00 2001
From: John Doty <john@d0ty.me>
Date: Sat, 1 Jun 2024 05:57:16 -0700
Subject: [PATCH] Allow the generator to be a little more declarative

---
 grammar.py |  4 ++--
 parser.py  | 16 ++++++++++++++--
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/grammar.py b/grammar.py
index 1801bfd..1ecf61f 100644
--- a/grammar.py
+++ b/grammar.py
@@ -54,10 +54,11 @@ RSQUARE = Terminal("RightBracket")
 
 
 class FineGrammar(Grammar):
+    generator = GenerateLALR
+    start = "File"
 
     def __init__(self):
         super().__init__(
-            start="File",
             precedence=[
                 (Assoc.RIGHT, [EQUAL]),
                 (Assoc.LEFT, [OR]),
@@ -81,7 +82,6 @@ class FineGrammar(Grammar):
                 #
                 (Assoc.NONE, [self.is_expression]),
             ],
-            generator=GenerateLALR,
         )
 
     @rule("File")
diff --git a/parser.py b/parser.py
index 813d91d..4ad5683 100644
--- a/parser.py
+++ b/parser.py
@@ -1854,14 +1854,26 @@ class Grammar:
 
     def __init__(
         self,
-        start: str,
+        start: str | None = None,
         precedence: PrecedenceList | None = None,
-        generator: type[GenerateLR0] = GenerateLALR,
+        generator: type[GenerateLR0] | None = None,
     ):
+        if start is None:
+            start = getattr(self, "start", None)
+        if start is None:
+            raise ValueError(
+                "The default start rule must either be specified in the constructor or as an "
+                "attribute in the class."
+            )
+
         if precedence is None:
             precedence = getattr(self, "precedence", [])
         assert precedence is not None
 
+        if generator is None:
+            generator = getattr(self, "generator", GenerateLALR)
+        assert generator is not None
+
         precedence_table = {}
         for prec, (associativity, symbols) in enumerate(precedence):
             for symbol in symbols: