Return a blank integer in c - c

Question

I want to write a power function that prints "Unable to compute o^o" when asked to do so or return the integer result. how can I accomplish this?
My current code prints the error statement as well as the result statement.
My code:
#include <stdio.h>
double power(int base,int n);
int main() {
int no1,no2;
printf("Enter two numbers:\n");
printf("If you want to compute x^y enter x y\n");
scanf("%i%i", &no1, &no2);
printf("The value of %i^%i is %f", no1, no2, power(no1,no2));
return 0;
}
double power(int base, int n) {
double result = 1;
if( n == 0 && base == 0){
printf("Unable to compute 0^0\n");
}
else if( n == 0 && base != 0) {
result = 1;
}
else if( n>0 ){
for(n ; n>0 ; n--) {
result = result*base;
}
}
else if( n<0 ){
int temp = -n;
result = power(base,temp);
result = (float)1.0/result;
}
return result;
}
EDIT: I am actually a novice. I am in the first chapter of K&R where I found a power function. I wanted to improve that thing and found this hurdle. Hence please provide resources if possible so that I understand your answers.

Answer 1

#BartoszMarcinkowski gives you the correct answer, as an alternative (if you can't pass an extra variable) you can return NAN and check the result with isnan().
In computing, NaN, standing for not a number, is a numeric data type
value representing an undefined or unrepresentable value, especially
in floating-point calculations.
#include <stdio.h>
#include <math.h>
double power(int base,int n);
int main(void)
{
double f;
f = power(2, 2);
if (isnan(f)) {
printf("Unable to compute power\n");
} else {
printf("%f\n", f);
}
return 0;
}
double power(int base, int n) {
double result = 1;
if( n == 0 && base == 0){
return NAN;
}
...
return result;
}

Answer 2

It is common for C functions to return 0 on success or error code in case of failure.
#include <stdio.h>
int power(int base,int n, double *result);
int main() {
int no1, no2;
printf("Enter two numbers:\n");
printf("If you want to compute x^y enter x y\n");
scanf("%i%i", &no1, &no2);
double result;
int error = power(no1, no2, &result);
if(error == 0)
printf("The value of %i^%i is %f\n", no1, no2, result);
return 0;
}
int power(int base, int n, double *result) {
*result = 1;
if(n == 0 && base == 0){
printf("Unable to compute 0^0\n");
return 1;
} else if(n == 0 && base != 0) {
*result = 1;
return 0;
} else if(n>0){
for(; n>0 ; n--) {
*result = *result*base;
}
return 0;
} else if(n < 0){
int temp = -n;
power(base,temp, result);
*result = (float) 1.0 / *result;
return 0;
}
return 1;
}

Answer 3

Note : My answer is in reference to the user's post saying that he is
a novice at learning C, so I have assumed that he might not have yet
be comfortable dealing with pointers.
You can have an error flag in your code that tells the main function that an error has occurred.
You can use a global integer, that is common to all functions of your program to inform of errors in code.
After calling the power function, you check whether the error FLAG is set, which means errors have occurred. So you print the error message instead of the result.
What value you should use for showing a error has occurred is arbitrary. In most cases, a non-zero (sometimes negative) value can indicate the specific error. For example:
FLAG = -1 might indicate invalid input
FLAG = -2 might indicate invalid operation
And so on. etc. Here I have chosen FLAG = non-zero value to mean error has occurred.
#include <stdio.h>
double power(int base,int n);
--> char FLAG = 0;
int main() {
int no1,no2;
---- your code ---
double and = power(no1,no2);
--> if (char) {
printf("error : both values cannot be negative);
char = 0;
} else {
printf("The value of %i^%i is %f", no1, no2, ans);
}
return 0;
}
double power(int base, int n) {
---- your code ---
if( n == 0 && base == 0){
printf("Unable to compute 0^0\n");
--> FLAG = -1;
return 0;
}
else if( n == 0 && base != 0) {
result = 1;
}
else ---- your code ---
}