void main(void)
{
double opn1, opn2; /* working operands */
char s[LINE_SIZE]; /* input line buffer */
char opr; /* working operator */
char *p; /* buffer cursor */
printf("\nPrefix Form Evaluator");
printf("\n=====================");
printf("\n\nInput --> ");
gets(s);
initial(); /* initial stack */
for (p = s; *p != '\0'; p++) /* for each character */
if (is_opr(*p)) /* is is an operator ? */
push_opr(*p); /* YES, push. */
else if (isdigit(*p)) { /* is it an operand ? */
opn2 = *p - '0'; /* YES, convert to double */
while (stack_top() == OPERAND) {
opn1 = pop_opn(); /* for all of its */
opr = pop_opr(); /* buddy, compute */
opn2 = compute(opr, opn1, opn2);
}
push_opn(opn2); /* then push the result */
}
printf("\nResult = %lf", pop_opn());
}
real calc_check(int check,const char * exp)
{
real opd_stack[STACK_SIZE];
int opr_stack[STACK_SIZE];
int opd_size = 0,opr_size = 0;
int state = 1/*,i*/;
extern VAR * find_var (const char *);
if (check)
{
match_exp(exp);
l_get_token();
if (token_type!=TT_LINE_END)
{
merror_msg("illegal expr");
}
}
pline = exp;
while(1)
{
l_get_token();//puts(token);SHOW_STACK;
// exit
if (token_type==TT_LINE_END)
{
break;
}
else if (token_type==TT_ID)
{
VAR * v;ARRAY * a;
if (state!=1 && !check)
{
l_put_back();
break;
}
v = find_var(token);
if (v!=NULL)
{
push_opd(v->value);
move2(2);
continue;
}
a = find_array (token);
if (a!=NULL)
{
int index;
l_get_token();//skip (
index = (int)calc_check(FALSE,pline);
// delete this line,calc_check call skip ( automatically
//l_get_token();//skip )
push_opd(get_element(a,index));
move2(2);
continue;
}
merror_msg("Unrecognized identifier '%s'",token);
}
// constant
else if (token_type==TT_INT || token_type==TT_FLOAT)
{
push_opd((real)atof(token));
move2(2);
}
// operator
else if (IS_OPR(token_type))
{
// neg "-" judgement
if (token_type==OPR_SUB && state==1)
{
token_type = OPR_NEG;
}
//
if (opr_size>0 &&
opr_stack[opr_size-1]!=TT_LBK &&
priority(token_type) <= priority(opr_stack[opr_size-1]))
{
real result;
result = calc_pop(opd_stack,opr_stack,&opd_size,&opr_size);
push_opd(result);
}
push_opr(token_type);
move2(1);
}
// process '(' and ')'
else if (token_type==TT_LBK)
{
push_opr(token_type);
}
else if (token_type==TT_RBK)
{
while(opr_stack[opr_size-1] /* top */ != TT_LBK && opr_size > 0)
{
real result;
result = calc_pop(opd_stack,opr_stack,&opd_size,&opr_size);
push_opd(result);
}
if (opr_stack[opr_size-1] /* top */ == TT_LBK)
{
opr_size--; // pop '('
}
else // funcition call end
{
break;
}
}
// built-in function call
else if (IS_RESWORD(token_type))
{
int argc = token_ext,i;
real result;
FUNCTION func = get_func(token_type);
//printf("call <%s>\n",token);
// skip '('
l_get_token ();
// get all arg and push them in stack
for (i=0;i<argc;++i)
{
result = calc_check(FALSE,pline);
push_opd(result);
//printf("[%d] |%.4lf|\n",i,result);
}
// call func
result = func(opd_stack + opd_size - argc);
// pop args
opd_size -= argc;
// push result
push_opd(result);
//printf("call end\n");
}
else
{
if (check)
merror_illegal_token();
else
{
l_put_back();
break;
}
}
}
// pop up all
while(opr_size > 0)
{
real result;
result = calc_pop(opd_stack,opr_stack,&opd_size,&opr_size);
push_opd(result);
}
if (opd_size != 1)
{
merror_msg("calc:unknown error!");
}
return opd_stack[0];
}
