1 files changed, 13 insertions, 6 deletions

diff --git a/impl/EquationSystem.g b/impl/EquationSystem.g
index 6db7045..3a6598a 100644
--- a/impl/EquationSystem.g
+++ b/impl/EquationSystem.g
@@ -3,27 +3,34 @@ grammar EquationSystem;
 options {
   language=C;
   output=AST;
+  backtrack=true;
 }
 
 tokens {
-  SYSTEM = 'system' ;
   PLUS = '+' ;
   SUB = '-' ;
   MULT = '*' ;
+  COMMA = ';' ;
+  GUARD = 'guard' ;
+  GREATER_EQUAL = '>=' ;
+  QUESTION_MARK = '?' ;
   MAXIMUM = 'max' ;
   MINIMUM = 'min' ;
   NEWLINE = '\n' ;
 }
 
-equation_system : equation ( NEWLINE! + equation  )* (NEWLINE!) *;
-equation : VARIABLE '='! maxExpr;
+equation_system : equation ( NEWLINE! + equation  )* (NEWLINE!)* ;
+equation : VARIABLE '='! maxExpr ;
 
-maxExpr : MAXIMUM^ '('! minExpr ( ','! minExpr )* ')'! | minExpr;
+maxExpr : MAXIMUM^ '('! minExpr ( ','! minExpr )* ')'! | minExpr ;
 minExpr : MINIMUM^ '('! maxExpr ( ','! maxExpr )* ')'! | expr ;
 
-expr : term ( (PLUS | MULT | SUB)^ term )* ;
+expr : '(' expr GREATER_EQUAL expr QUESTION_MARK expr ')' -> ^(GUARD expr expr expr)
+     | term ( (PLUS | MULT | SUB | COMMA)^ expr )* ;
 
-term : NUMBER | VARIABLE ;
+term : NUMBER
+     | VARIABLE
+     | '('! expr ')'! ;
 
 
 NUMBER : (DIGIT)+ ;