%{
/*
 *               Bison source of a
 *               parser for the Oberon-2 Programming Language
 *
 *       Author: James Power,
 *  Affiliation: Dept. of Computer Science, National University of Ireland,
 *               Maynooth, Co. Kildare, Ireland.
 * Last Revised: 24 November 1998
 *
 *     Based on: "The Programming Language Oberon"
 *               H. Mossenbock, N. Wirth, ETH Zurich, 1992-1996
 *
 * For more information on Oberon see http://www.oberon.ethz.ch/language.html
 */
 
  // The lex variables
  extern char *yytext;
  extern int yylineno;
  int yyerror(char *msg);

%}

%token ident
%token CONSTchar CONSTstring     CONSTnumber
%token ARRAY     IMPORT     RETURN
%token OBEGIN    IN         THEN
%token BY        IS         TO
%token CASE      LOOP       TYPE
%token CONST     MOD        UNTIL
%token DIV       MODULE     VAR
%token DO        NIL        WHILE
%token ELSE      OF         WITH
%token ELSIF     OR
%token END       POINTER
%token EXIT      PROCEDURE
%token FOR       RECORD
%token IF        REPEAT

%token ASSIGN    LTEQ GTEQ DOTDOT

%nonassoc '='  '#'  '<'  LTEQ  '>'  GTEQ  IN  IS
%nonassoc UPLUS UMINUS
%left '+'  '-'  OR
%left '*'  '/'  DIV  MOD  '&'


%%

Module       : 
{ yydebug=0; }
  MODULE ident ';' optImportList DeclSeq optStatBody END ident '.'
;

optImportList   : 
  IMPORT ImportSpecList ';'
| /* Empty */
;

ImportSpecList : 
  ImportSpec ',' ImportSpecList
| ImportSpec
;

ImportSpec    :
  ident ASSIGN ident
| ident
;

optStatBody  :
  OBEGIN StatementSeq
| /* Empty */
;

DeclSeq      : 
  CVT_List ProcList
;

CVT_List      :
  CONST ConstDeclList CVT_List 
| TYPE  TypeDeclList  CVT_List
| VAR   VarDeclList   CVT_List
| /* Empty */
;

ProcList     :
  ProcDecl ';' ProcList
| ForwardDecl ';' ProcList
| /* Empty */
;

ConstDeclList :
  IdentDef '=' ConstExpr ';' ConstDeclList
| /* Empty */
;

TypeDeclList : 
  IdentDef '=' Type ';' TypeDeclList
| /* Empty */
;

VarDeclList  : 
  IdentDefList ':' Type ';' VarDeclList
| /* Empty */
;

ProcDecl     : 
  PROCEDURE optReceiver IdentDef optFormalPars ';' 
            DeclSeq optStatBody 
  END ident
;

ForwardDecl  : 
  PROCEDURE '^' optReceiver IdentDef optFormalPars
;

optFormalPars : 
  '(' optFPList ')' ':' Qualident
| '(' optFPList ')' 
| /* Empty */
;

optFPList    :
  FPList
| /* Empty */
;

FPList       :
  FormalParam ';' FPList
| FormalParam
;

FormalParam  :
  optVAR IdentList ':' Type 

IdentList    :
  ident
| ident ',' IdentList
;

optReceiver     : 
  '(' optVAR ident ':' ident ')'
| /* Empty */
;

optVAR       :
  VAR
| /* Empty */
;
 
Type         : 
  Qualident
| ARRAY ConstExprList OF Type 
| ARRAY               OF Type 
| RECORD '('Qualident')' FieldList END
| RECORD                 FieldList END
| POINTER TO Type
| PROCEDURE optFormalPars
;

ConstExprList :
  ConstExpr ',' ConstExprList
| ConstExpr
;

FieldList    : 
  IdentDefList ':' Type ';' FieldList
| IdentDefList ':' Type
| /* Empty */
;

StatementSeq : 
  Statement ';' StatementSeq
| Statement
| /* Empty */
;

Statement    : 
  Designator ASSIGN Expr 
| Designator
| IF Expr THEN StatementSeq ElifList optElse END 
| CASE Expr OF CaseList optElse END 
| WHILE Expr DO StatementSeq END 
| REPEAT StatementSeq UNTIL Expr 
| FOR ident ASSIGN Expr TO Expr optBY DO StatementSeq END 
| LOOP StatementSeq END
| WITH GuardStatList optElse END
| EXIT 
| RETURN Expr
| RETURN
;

ElifList    :
  ELSIF Expr THEN StatementSeq ElifList
| /* Empty */
;

optElse      :
  ELSE StatementSeq
| /* Empty */
;

optBY        :
  BY ConstExpr
| /* Empty */
;
CaseList     :
  Case
| Case '|' CaseList
;

Case         : 
  CaseLabelList ':' StatementSeq
| /* Empty */
;

CaseLabelList :
  CaseLabels
| CaseLabels ',' CaseLabelList
;

CaseLabels   : 
  ConstExpr 
| ConstExpr DOTDOT ConstExpr
;

GuardStatList :
  Guard DO StatementSeq '|' GuardStatList
| Guard DO StatementSeq 
;

Guard        : 
  Qualident ':' Qualident
;

ConstExpr    : 
  Expr
;

Expr         : 
/* Relations */
  Expr '=' Expr
| Expr '#' Expr
| Expr '<' Expr
| Expr LTEQ Expr
| Expr '>' Expr
| Expr GTEQ Expr
| Expr IN Expr
| Expr IS Expr
/* Unary (prefix) Operators */
| '+' Expr %prec UPLUS
| '-' Expr %prec UMINUS
/* Additive Operators */
| Expr '+' Expr
| Expr '-' Expr
| Expr OR Expr
/* Multiplicative Operators */
| Expr '*' Expr
| Expr '/' Expr
| Expr DIV Expr
| Expr MOD Expr
| Expr '&' Expr
| Factor
;

Factor       : 
  Designator
| CONSTnumber 
| CONSTchar 
| CONSTstring 
| NIL 
| Set 
| '(' Expr ')' 
| '~' Factor
;

Set          : 
  '{' optElementList '}'
;

optElementList :
  ElementList
| /* Empty */
;

ElementList :
  Element ',' ElementList
| Element 
;

Element      : 
  Expr 
| Expr DOTDOT Expr
;

Designator   : 
  ident optSuffix
;

optSuffix :
  '.' ident  optSuffix
| '[' optExprList ']'  optSuffix
| '^'  optSuffix
| '(' optExprList ')' optSuffix  /* NB - too wide! (avoiding ambiguity) */
| /* Empty */
;

optExprList     : 
  ExprList 
| /* Empty */
;

ExprList     : 
  Expr 
| Expr ',' ExprList
;

IdentDefList    : 
  IdentDef 
| IdentDef ',' IdentDefList
;

Qualident    : 
  ident
| ident '.' ident
;
IdentDef     : 
  ident 
| ident '*' 
| ident '-'
;


%%

int yyerror(char *msg)
{
  printf("%s at line %d with [%s]\n",msg,yylineno,yytext);
}

int main()
{
  int res = yyparse();
  if (res==0)
    printf("Successful parse\n");
  else
    printf("Encountered errors\n");
  exit(res);
}