C boolean function comparing 2 Strings alphabeticly - c

Question

So I am trying to compare 2 strings and if the first one (x) is smaller than the second one the method twoStrComp should return true, else it should be false.
This is my code, although when I try to run it on my terminal nothing comes up...
As if it ignored my code.. Also I was wondering if it would be more efficient with pointers but I was unsure of how to declare them, can I do twoStrComp(*x,*y)?
ORIGINAL CODE:
#include <stdio.h>
#include <stdbool.h>
bool twoStrComp(char[], char[]);
int main(void)
{
char x[]= "test";
char y[]= "another";
twoStrComp(x,y);
}
bool twoStrComp(char string1[], char string2[] )
{
int i=0, flag=0;
while(flag==0)
{
if (string1[i]<string2[i])
{
flag=-1;
}
else if (string1[i]==string2[i])
{
flag=0;
i++
}
else
{
return 1;
}
}
return flag;
}
new VERSION:
bool twoStrComp(char[], char[]);
int main(void)
{
char x[]= "atest";
char y[]= "another";
bool ans = twoStrComp(x,y);
printf("%s", ans ? "true" : "false");
}
bool twoStrComp(char string1[], char string2[] )
{
int i=0, flag=0;
bool value = false;
while(flag==0) {
if (string1[i]>string2[i])
{
flag=1;
value = false;
}
else if (string1[i]<string2[i])
{
flag=-1;
value = true;
}
else if (string1[i]==string2[i])
{
return 0;
value = true;
}
else
{
i++;
}
}
if(flag == 1)
return (value == false);
if(flag == -1)
return (value == true);
return value;
}

Answer 1

So I am trying to compare 2 strings and if the first one (x) is smaller than the second one the method twoStrComp should return true, else it should be false.
I suggest a better name for your function. It is no generic compare function but it's more a isSmaller function. You don't care about separate cases for identical or larger values.
This is my code, although when I try to run it on my terminal nothing comes up
If you want to see anything on your console, you need to print something. You can use printf for that purpose.
Also I was wondering if it would be more efficient with pointers but I was unsure of how to declare them, can I do twoStrComp(*x,*y)?
If you want to pass pointers, you can declare it like this:
bool twoStrComp(const char *x, const char *y)
But....
Passing arrays as parameters results in passing pointers anyway. The array decays to pointers when used in parameter list of a function. You won't see any performance improvement.
Regarding your code...
I refer to the version listed as version 2 in edit history.
You return 1 or -1. As you use type bool for return type, you should think about using TRUE or FALSE. Or at least return 0 in some case.
Setting flag=0; does not have any sense. If it wasn't 0 before, you would have left the loop.
You don't check whether you compare beyond the end of the strings.
A version that fixes those problems and includes some test cases could look like this:
#include <stdbool.h>
#include <stdio.h>
bool twoStrComp(char string1[], char string2[]);
int main(void)
{
char x[]= "test";
char y[]= "another";
bool isSmaller = twoStrComp(x,y);
printf("Is x(%s) smaller than y(%s)? %s\n", x, y, isSmaller ? "YES" : "NO");
isSmaller = twoStrComp(y,x);
printf("Is y(%s) smaller than x(%s)? %s\n", y, x, isSmaller ? "YES" : "NO");
char x2[]= "aaa";
char y2[]= "aab";
isSmaller = twoStrComp(x2,y2);
printf("Is x2(%s) smaller than y2(%s)? %s\n", x2, y2, isSmaller ? "YES" : "NO");
isSmaller = twoStrComp(y2,x2);
printf("Is y2(%s) smaller than x2(%s)? %s\n", y2, x2, isSmaller ? "YES" : "NO");
isSmaller = twoStrComp(x2,x2);
printf("Is x2(%s) smaller than x2(%s)? %s\n", x2, x2, isSmaller ? "YES" : "NO");
}
bool twoStrComp(char string1[], char string2[])
{
int i=0;
while (true)
{
if (string1[i] < string2[i])
return true; // First one smaller than second one...
else if (string1[i] > string2[i])
return false; // First one larger than second one...
else if (!string1[i])
return false; // identical and end of strings reached.
else
i++; // identical, not yet decided.
}
// We cannot get here, but the compiler complains...
return false;
}