why isnt this working?

[spiroth10]

I haven't bothered with c/c++ in a long time. After going to revisit it, I ended up with this not working.

I havent the slightest idea why, but the if statements arent evaluating the variable as a character, although if I try to printf(); out the variable it clearly gives me a y or n.

#include <stdio.h>

char ans;
   
int main(){
    
   printf("are you cool? y/n\n");
   scanf ("%s", &ans);  
   if (ans == "y") {
      printf("yes\n");
   }
   else if (ans == "n") {
      printf("no\n");
   }
   else { 
      printf("your choice was not an answer, either y or n are\n");
   }
   getchar();
   return 0;
} 

[ih8censorship]

What was happening, was you were trying to compare a char value with a memory location (what is in the double quotes) you can either replace what you have in your if with ans=='y' and ans=='n' (which checks the literal character value) or you could use C strings

Code

GeSHi (c):
#include <stdio.h>
#include <string.h>
 
char ans;
 
int main(){
 
   printf("are you cool? y/n\n");
   scanf ("%s", &ans);  
   if (strcmp(&ans,"y")==0) {
      printf("yes\n");
   }
   else if (strcmp(&ans,"n")==0) {
      printf("no\n");
   }
   else { 
      printf("your choice was not an answer, either y or n are\n");
   }
   getchar();
   getchar();//extra one so it halts program long enough to see the output
   return 0;
} 
 
Created by GeSHI 1.0.7.18

[adeyblue]

Code

GeSHi (c):
char ans;
...
scanf ("%s", &ans);
...
if (strcmp(&ans,"y")==0) {
...
else if (strcmp(&ans,"n")==0) {
 
Created by GeSHI 1.0.7.18

Noooo, you're as bad as each other You should use %c with scanf to read a single char, %s adds the NUL terminator to the buffer which would overflow the single char. As for strcmp, yes it takes a char*, but remember C-strings have to be NUL-terminated which a single char obviously isn't (well, unless you enter NUL in the scanf). It's much easier to just replace it with a simple if(ans == 'y')

[FrozenKnight]

adeyblue the method h8 mentioned is fine for a single char comparison. in fact I've used it for comparing up to 4 chars (on 32 bit processors). and I've seen variants of this method taught in just about every C book I've seen.

[C-Man]

it's still overflowing tho , you shouldn't do that , use %c as adeyblue said

[adeyblue]

If you use:

Code

GeSHi (c):
char ans;
int ret;
 
scanf ("%s", &ans);  
ret = strcmp(&ans,"y");
 
Created by GeSHI 1.0.7.18

then it'll technically work since the NUL will be stored in the byte after ans, however it's also very incorrect as fitting two chars in the space of one is a buffer overflow. If you correctly read the char with %c then the strcmp will no longer do what is expected as it goes on to take into account whatever trash is in memory after ans.

[FrozenKnight]

Code

GeSHi (c):
char ans;
int ret;
 
scanf ("%c", &ans);  
ret = ans - 'y'
Created by GeSHI 1.0.7.18

does exactly the same thing, without overflow.
but

Code

GeSHi (c):
if (ans == 'y')
Created by GeSHI 1.0.7.18

is considered more correct.
or

Code

GeSHi (c):
switch ans
{
  case 'y':
    /*code here*/
    break;
}
Created by GeSHI 1.0.7.18

the only overflow is going to be in the scanf statement, which still is in your code adeyblue. checking a char against a char or array will not result in overflow. just possible unpredictable results.

[spiroth10]

Thanks for your help guys, its been like 2 years since I've bothered much with C/C++ and now I'm getting back into it again. You've helped me a great deal