From b42098ef8cc477459d1926bf08bd8400c6ecbfea Mon Sep 17 00:00:00 2001
From: Peter Wu <peter@lekensteyn.nl>
Date: Sat, 7 May 2016 20:04:10 +0200
Subject: Attempt to convert grammar to LL(1)

Needs more verification, but the idea is that the expressions with
lowest precedence (+) should be the first one in the parse tree
(implying that non-terminals with highest precedence should be just
above a terminal).

Left-associativity is achieved by the trick in section 2.3.1 of
Intro2CD which results in the left operand being recursed instead of the
right one.
---
 grammar-ll1.txt | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/grammar-ll1.txt b/grammar-ll1.txt
index 9487bd1..23c1abf 100644
--- a/grammar-ll1.txt
+++ b/grammar-ll1.txt
@@ -12,12 +12,14 @@ context-free syntax
   STATEMENT ::= ID ":=" EXP
 
 context-free syntax
-  EXP ::= ID
-  EXP ::= NAT
-  EXP ::= EXP "+" EXP {left}
-  EXP ::= EXP "*" EXP {left}
-  EXP ::= "-" EXP
-  EXP ::= "(" EXP ")"
+  EXP ::= EXP "+" PROD-EXP
+  EXP ::= PROD-EXP
+  PROD-EXP ::= EXP "*" SINGLE-EXP
+  PROD-EXP ::= SINGLE-EXP
+  SINGLE-EXP ::= "-" EXP
+  SINGLE-EXP ::= ID
+  SINGLE-EXP ::= NAT
+  SINGLE-EXP ::= "(" EXP ")"
 
 lexical syntax
   ID ::= [a-z] ID'
@@ -34,8 +36,3 @@ lexical syntax
   LAYOUT ::= " " LAYOUT
   LAYOUT ::= "\n" LAYOUT
   LAYOUT ::=
-
-context-free priorities
-  EXP ::= "-" EXP >
-    EXP ::= EXP "*" EXP >
-    EXP ::= EXP "+" EXP
-- 
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