%{
#include <stdio.h>
extern void yyerror(char *);
%}
%token YASSIGN
%token YBEGIN
%token YCOLON
%token YCOMMA
%token YCONST
%token YDOT
%token YEND
%token YEQUALS
%token YIDENTIFIER
%token YINTEGER
%token YINTNUMBER
%token YMULT
%token YPLUS
%token YPROGRAM
%token YSEMICOL
%token YVAR

%start pascalProgram

%%
pascalProgram 
	: programHeading YSEMICOL block1 YDOT
		{ printf("parsing completed.\n"); }
	;
programHeading
	: YPROGRAM YIDENTIFIER
	;
block1
	: constantDecl YSEMICOL block2
	;
constantDecl
	: YCONST YIDENTIFIER YEQUALS YINTNUMBER
	| constantDecl YSEMICOL YIDENTIFIER YEQUALS YINTNUMBER
	;
block2
	: variableDecl YSEMICOL block3
	;
variableDecl
	: YVAR variableIdList YCOLON YINTEGER
	;
variableIdList
	: YIDENTIFIER
	| variableIdList YCOMMA YIDENTIFIER
	;
block3
	: YBEGIN stmtList YEND
	;
stmtList
	: stmt YSEMICOL
	| stmtList stmt YSEMICOL
	;
stmt
	: variable YASSIGN simpleExpression
	;
variable
	: YIDENTIFIER
	;
simpleExpression
	: term
	| simpleExpression YPLUS term
	| simpleExpression YMULT term 
	;
term
	: YIDENTIFIER
	| YINTNUMBER
	;
%%
extern FILE *yyin;
void main()
{
	while(!feof(yyin)){
	   yyparse();
	}
}

void yyerror(s)
char *s;
{
	fprintf(stderr, "%s\n", s);
}