--description of the abstract syntax of ModulaX
--in ASDL v.1.2

module ModulaX
{
   program = (module)
   
   module = (identifier, block)
   
   block = (declaration*, stmt*)
   
   declaration = DECLCONST (identifier, typ?, expr)
   	       | DECLTYPE (typedeclaration)
   	       | DECLTYPEREC (typedeclaration*)
   	       | DECLVAR (identifier*, typ?, expr?)
   	       | DECLPROC (identifier, signature, block)
   
   typedeclaration = (identifier, typ)
   
   signature = (formal*, typ?)
   
   formal = (identifier*, mode?, typ)
   
   mode = VALUE | VAR
   
   stmt = STMTBLOCK (block)
   	| STMTASSIGN (expr lhs, expr rhs)
   	| STMTCALL (proccall)
   	| STMTEXIT
   	| STMTEVAL (expr)
   	| STMTFOR (identifier index, expr from, expr to, expr? by, stmt*)
   	| STMTIF (expr condition, stmt* thenpart, elsifclause*, elseclause?)
   	| STMTLOOP (stmt*)
   	| STMTREAD (string format, expr*)
   	| STMTREPEAT (stmt*, expr condition)
   	| STMTRETURN (expr?)
   	| STMTWHILE (expr condition, stmt*)
   	| STMTWRITE (string format, expr*)
   
   elsifclause = (expr condition, stmt*)
   
   elseclause = (stmt*)
   
   typ = TYPARRAY (typ* indextypes, typ elementtype)
       | TYPRECORD (field*)
       | TYPSUBRANGE (expr lowbound, expr highbound)
       | TYPID (identifier)
       | TYPREF (typ)
   
   field = (identifier, typ)
   
   expr = EXPRBINARY (expr, binary, expr)
   	| EXPRUNARY (unary, expr)
   	| EXPRID (identifier)
   	| EXPRINT (int)
   	| EXPRREAL (real)
   	| EXPRTEXT (string)
   	| EXPRRECSEL (expr, identifier)
   	| EXPRARRAYREF (expr, expr*)
   	| EXPRPROCCALL (proccall)
   	| EXPRDEREF (expr)
   	| EXPRNEW (typ)
   	| EXPRNIL (typ)
   
   proccall = (expr, expr*)
   
   binary = OR | AND | EQUAL | NEQUAL | LESS | GREATER | LE | GE 
   	  | ADD | SUB | MUL | DIV | MOD
   
   unary = NOT | UPLUS | UMINUS
   
   real = (int mantissa, int exp)  
}