static void evalExpression(Parser *p){
evalTerm(p);
while(p->s[0]=='+' || p->s[0]=='-'){
int sign= p->s[0]=='-';
double d;
p->s++;
evalTerm(p);
d= pop(p);
if(sign) d= -d;
push(p, d + pop(p));
}
}
/*
* Returns cos(x). Good for about (-30, 30).
*/
double cos(double x)
{
double result = 0;
for (int i = 0; i < NUM_TERMS; i++)
{
result += pow(-1.0, i) * evalTerm(x, 2*i);
}
return result;
}
/*
* Returns e^x. Good for about (-10, 700).
*/
double e(double x)
{
double result = 0;
for (int i = 0; i < NUM_TERMS; i++)
{
result += evalTerm(x, i);
}
return result;
}
static int
evalTerm(char *s,
struct tr *tr,
int *lenPtr,
value * covPtr)
{
int len;
int skip;
len = 0;
while (isspace(s[len]))
++len;
switch (s[len]) {
case '\0':
fprintf(stderr, "empty subexpression\n");
return -1;
case '(':
++len;
if (evalConj(s + len, tr, &skip, covPtr) == -1)
return -1;
len += skip;
while (isspace(s[len]))
++len;
if (s[len] != ')') {
fprintf(stderr, "unballanced parenthesis\n");
free(*covPtr);
return -1;
}
++len;
*lenPtr = len;
break;
case '!':
++len;
if (evalTerm(s + len, tr, &skip, covPtr) == -1)
return -1;
len += skip;
doNot(*covPtr, tr->covCount);
*lenPtr = len;
break;
default:
if (evalNames(s + len, tr, &skip, covPtr) == -1)
return -1;
len += skip;
*lenPtr = len;
break;
}
return 0;
}
static int
evalDisj(char *s,
struct tr *tr,
int *lenPtr,
value * covPtr)
{
int len;
int skip;
value cov1;
value cov2;
len = 0;
if (evalTerm(s + len, tr, &skip, &cov1) == -1)
return -1;
len += skip;
while (isspace(s[len]))
++len;
while (s[len] == '&') {
++len;
if (evalTerm(s + len, tr, &skip, &cov2) == -1) {
free(cov1);
return -1;
}
len += skip;
doDisj(cov1, cov2, tr->covCount);
free(cov2);
while (isspace(s[len]))
++len;
}
*covPtr = cov1;
*lenPtr = len;
return 0;
}
static double evalExpression(Parser *p){
double ret= 0;
if(p->stack_index <= 0) //protect against stack overflows
return NAN;
p->stack_index--;
do{
ret += evalTerm(p);
}while(*p->s == '+' || *p->s == '-');
p->stack_index++;
return ret;
}
