From 0e70fc94f8c041a9c656be9a73425ced7a6858f2 Mon Sep 17 00:00:00 2001
From: yhirose <yuji.hirose.bug@gmail.com>
Date: Wed, 29 Jul 2015 20:15:09 -0400
Subject: [PATCH] Added pl0.peg.

---
 grammar/pl0.peg | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 grammar/pl0.peg

diff --git a/grammar/pl0.peg b/grammar/pl0.peg
new file mode 100644
index 0000000..5da96bd
--- /dev/null
+++ b/grammar/pl0.peg
@@ -0,0 +1,35 @@
+
+program    <- block '.' _
+
+block      <- const var procedure statement
+const      <- ('CONST' _ ident '=' _ number (',' _ ident '=' _ number)* ';' _)?
+var        <- ('VAR' _ ident (',' _ ident)* ';' _)?
+procedure  <- ('PROCEDURE' _ ident ';' _ block ';' _)*
+
+statement  <- (assignment / call / statements / if / while / write)?
+assignment <- ident ':=' _ expression
+call       <- 'CALL' _ ident
+statements <- 'BEGIN' _ statement (';' _ statement )* 'END' _
+if         <- 'IF' _ condition 'THEN' _ statement
+while      <- 'WHILE' _ condition 'DO' _ statement
+out        <- '!' _ expression
+
+condition  <- odd / compare
+odd        <- 'ODD' _ expression
+compare    <- expression compare_op expression
+compare_op <- < '=' / '#' / '<=' / '<' / '>=' / '>' > _
+
+expression <- sign term (term_op term)*
+sign       <- < [-+]? > _
+term_op    <- < [-+] > _
+
+term       <- factor (factor_op factor)*
+factor_op  <- < [*/] > _
+
+factor     <- ident / number / '(' _ expression ')' _
+
+ident      <- < [a-z] ([a-z] / [0-9])* > _
+number     <- < [0-9]+ > _
+
+~_         <- [ \t\r\n]*
+