main()
{
char *pc;
char buf[256];
double result;
while(1)
{
printf("Enter Expression. Example: 2 3 4 + *(= (3+4)*2). ctrl + C to exit:\n");
fgets(buf, 256, stdin);
eval_rpn(&result, buf);
printf("result = %f\n", result);
}
}
int evaluate_RPN_expression(const char *expression)
{
int i;
for (i = 0; expression[i] != '\0'; i++) {
printf("%c\n", expression[i]);
if (expression[i] >= '0' && expression[i] <= '9') {
push(expression[i] - '0');
}
else if (expression[i] == ' ')
continue;
else if (expression[i] == '=') {
return pop();
}
else {
eval_rpn(expression[i]);
}
}
return pop();
}
static double eval_rpn(int *equat) {
int i;
double temx, temy, temz;
union /* WARNING -- ASSUMES 32 bit int and 64 bit double */
{
struct {
int int1;
int int2;
} pieces;
struct {
double z;
} num;
} encoder;
while ((i = *equat++) != ENDEXP) {
switch (i) {
case NUMSYM:
encoder.pieces.int2 = *equat++;
encoder.pieces.int1 = *equat++;
PUSH(encoder.num.z);
break;
case ENDFUN:
i = *equat++;
uptr -= i;
break;
case MYIF: {
int ijmp;
temx = POP;
ijmp = *equat++;
if (temx == 0.0)
equat += ijmp;
break;
}
case MYTHEN: {
int ijmp = *equat++;
equat += ijmp;
break;
}
case MYELSE:
break;
case ENDDELSHFT:
temx = POP;
temy = POP;
temz = POP;
PUSH(do_delay_shift(temx, temy, temz));
break;
case ENDDELAY:
temx = POP;
temy = POP;
PUSH(do_delay(temx, temy));
break;
case ENDSHIFT:
temx = POP;
temy = POP;
PUSH(do_shift(temx, temy));
break;
case ENDISHIFT:
temx = POP;
temy = POP;
PUSH(do_ishift(temx, temy));
break;
case SUMSYM: {
int high;
int low;
int ijmp;
double sum;
temx = POP;
high = (int)temx;
temx = POP;
low = (int)temx;
ijmp = *equat++;
sum = 0.0;
if (low <= high) {
for (int is = low; is <= high; is++) {
constants.elems[SumIndex] = (double)is;
sum += eval_rpn(equat);
}
}
equat += ijmp;
PUSH(sum);
break;
}
case ENDSUM:
return (POP);
case INDXCOM:
PUSH(0.0);
break;
default: {
int it = i / MAXTYPE;
int in = i % MAXTYPE;
switch (it) {
case FUN1TYPE:
PUSH(expr_fun1[in](POP));
break;
case FUN2TYPE:
switch (in) {
case 0:
temx = POP;
temy = POP;
PUSH(temx + temy);
break;
case 1:
temx = POP;
temy = POP;
PUSH(temy - temx);
break;
case 2:
temx = POP;
temy = POP;
PUSH(temx * temy);
break;
case 3:
temx = POP;
if (temx == 0.0)
temx = DOUB_EPS;
temy = POP;
PUSH(temy / temx);
break;
default:
temx = POP;
temy = POP;
PUSH(expr_fun2[in](temy, temx));
break;
}
break;
case CONTYPE:
PUSH(constants.elems[in]);
break;
case NETTYPE:
PUSH(network_value(POP, in));
break;
case TABTYPE:
PUSH(lookup(POP, in));
break;
case USTACKTYPE:
/* ram: so this means ustacks really do need to be of USTACKTYPE */
PUSH(ustack[uptr - 1 - in]);
break;
case KERTYPE:
PUSH(ker_val(in));
break;
case VARTYPE:
PUSH(variables.elems[in]);
break;
/* indexes for shift and delay operators... */
case SCONTYPE:
PUSH((double)(COM(CONTYPE, in)));
break;
case SVARTYPE:
PUSH((double)(COM(VARTYPE, in)));
break;
case UFUNTYPE:
i = *equat++;
for (int j = 0; j < i; j++) {
ustack[uptr] = POP;
uptr++;
}
PUSH(eval_rpn(ufuns.elems[in].rpn));
break;
}
break;
}
}
}
return (POP);
}
double evaluate(int *equat) {
uptr = 0;
stack_pointer = 0;
return (eval_rpn(equat));
}
