Made grammar a bit clearer

src/main/rascal/Syntax.rsc

@@ -54,9 +54,7 @@ syntax SubProgDecl        = 'function' Id Parameters ":" BasicType ";" VarDecl*
 
 syntax Parameters         = "(" ParameterList ")"
                           ;
-syntax ParameterList      = ParamList
-                          | ParameterList ";" ParamList
-                          ;
+syntax ParameterList      = ParamList (";" ParamList)*;
 /*
   Observe you can declare multiple parametrs in a single delcaration.
   Also note the 'var'. 'var' parameters are passed by reference, whereas non 'var' parameters
@@ -70,8 +68,7 @@ syntax ParamList          = 'var'? IdList ":" TypeSpec
 
 syntax CompoundStatement  = 'begin' StatementList? 'end';
 
-syntax StatementList      = Statement 
-                          | StatementList ";" Statement;
+syntax StatementList      = Statement (";" Statement)*;
 /*
   We have:
   1. Assignment statements