/*
    Very Simple Calculator
    $Id$
 */

#include <stdio.h>

static char *ptr,*last_ptr;
static int  value,lvalue;
static int  last_token;
static int  variable[48];

static int  expr();
static int  aexpr();
static int  mexpr();
static int  term();
static int  token();
static void  error(char *);


static int
token()
{
    int c,d;

    last_ptr = ptr;  /* for error position */
    c= *ptr;
    if(!c) {
        last_token = EOF;
        return last_token;
    }
    ptr++;
    if (c<=' ') {       /* comment */
        while(*ptr++);
            ptr--;
            last_token = EOF;
            last_ptr = ptr;
            return last_token;
    }

    if('0'<=c && c<='9') {     /* Decimal */
        d = c-'0';
        while((c= *ptr++)) {
            if('0'<=c && c<='9') {
                d = d*10 + (c - '0');
            } else {
                break;
            }
        }
        c && ptr--;
        value = d;
        last_token = '0';
        return last_token;

    } else if ('a'<=c && c<='z') {    /* variable */
        value = c-'a';                /* return variable reference */
        last_token = 'v';
        return last_token;
    } else {
        last_token = c;
        return last_token;
        return c;
    }
}

static int
expr()
{
    int d,assign;

    d = aexpr();
    assign = lvalue;
    switch(last_token) {
    case '>':
        d = (d > aexpr());
        return d;
    case '=':
        if(assign>=0) {
            d = expr(); 
            variable[assign] = d;
            return d;
        } else {
            error("Bad assignment");
            return 0;
        }
    case ')':
        return d;
    case EOF:
        return d;
    default:
        error("Bad expression");
        return d;
    }
}

static int
aexpr()
{
    int d;

    d = mexpr();
    switch(last_token) {
    case '-':
        d -= aexpr();
        return d;
    case '+':
        d += aexpr();
        return d;
    default:
        return d;
    }
}

static int
mexpr()
{
    int d;
    d = term();
    switch(last_token) {
    case '*':
        d *= mexpr();
        return d;
    case '/':
        d /= mexpr();
        return d;
    default:
        return d;
    }
}

static int
term()
{
    int d;

    lvalue= -1;
    token();
    if(last_token==EOF) {
        error("Term expected");
    }
    switch(last_token) {
    case '0':
        d = value;
        token();
        return d;
    case 'v':
        d = lvalue = value;
        token();
        return variable[d];
    case '(':
        d = expr();
        if(last_token != ')') {
            error("Unbalanced parenthsis");
        }
        token();
        return d;
    default:
        token();
        error("Unknown term");
        return 0;
    }
}

static int lineno = 0;

void
error(char *msg)
{
    fprintf(stderr,"%s on line %d\n",msg, lineno);
}

int
main()
{
    int d;
    char buf[BUFSIZ];

    while (fgets(buf,BUFSIZ,stdin)) {
        ptr = buf;
        d = expr();
        printf("%s = 0x%08x = %d\n",buf,d,d);
        fflush(stdout);
        lineno++;
    }
    return 0;
}