%{
#include <stdio.h>
#include <ctype.h>

int regs[26];
int base;

%}

%start list

%token DIGIT LETTER

/* do without precedence */

%%   /* beginning of rules section */

list	:	/* empty */
	|	list stat ';'
	|	list stat '\n'
	|	list '\n'
	|	list error '\n'
			{	yyerrok; }
	;
stat	:	expr
			{	printf( "%d\n",$1); }
	|	LETTER '=' expr
			{	regs[$1] = $3; }
	;
expr	:	expr '+' fctr
			{	$$ = $1 + $3; }
	|	expr '-' fctr
			{	$$ = $1 - $3; }
	|	fctr
	;
fctr	:	fctr '*' uexp
			{	$$ = $1 * $3; }
	|	fctr '/' uexp
			{	$$ = $1 / $3; }
	|	uexp
	;
uexp	:	'-' term
			{	$$ = - $2; }
	|	term
	;
term	:	'(' expr ')'
			{	$$ = $2; }
	|	LETTER
			{	$$ = regs[$1]; }
	|	number
	;
number	:	DIGIT
			{	$$ = $1; base = ($1==0) ? 8 : 10; }
	|	number DIGIT
			{	$$ = base * $1 + $2; }
	;

%%  /* start of program */
yylex(){
	int c;
	while((c=getchar()) == ' ') {/* skip blanks */};
	/* printf("read c= %c \n",c); */
	if(islower(c)){
		yylval=c-'a';
		return (LETTER) ;
		}
	if(isdigit(c)){
		yylval=c-'0';
		return (DIGIT) ;
		}
	return (c);
	}