do-while did not work

Question

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C++

#include <stdio.h>
#include <stdlib.h>

int main(void) {
    char again;
    do{
        printf("insert y or Y to repeat");
        fflush(stdout);
        scanf("%c",&again);
    }while(again=='y'||again=='Y');
}

i wrote this code to create a loop that when insert y or Y do the job again but did not work.when i enter first y the loop be end.

[edit]code blocks fixed[/edit]

Posted 26-Nov-12 19:39pm

ho_khalaf

Updated 27-Nov-12 11:59am

Nelek

v3

Add a Solution

5 solutions

Solution 2

you pressed 'y; and '\n'(Enter).two chars.
you can modify it

C++

#include <stdio.h>
#include <stdlib.h>

int main(void) {
    char again;
    do{
        printf("insert y or Y to repeat");
        fflush(stdout);
        scanf("%c",&again);
		getchar();
    }while(again=='y'||again=='Y');
}

Posted 26-Nov-12 21:27pm

midle110

Updated 27-Nov-12 13:01pm

v2

Comments

ho_khalaf 27-Nov-12 15:38pm

your code is good but when i use it like this did not work
#include <stdio.h>
#include <stdlib.h>

void scan_frac(int *num,int *denom);

int main(void){
int num1,denom1;
char again;
do{
scan_frac(&num1,&denom1);
printf("insert (y)to do another problem");
fflush(stdout);
again=getchar();
getchar();
}while(again=='y'||again=='Y');

return 0;
}

void scan_frac(int *num,int *denom){
int n,dn;
printf("insert numerator and denominator:");
fflush(stdout);
scanf("%d%d",&n,&dn);
*num=n;
*denom=dn;
}

Albert Holguin 27-Nov-12 19:01pm

Edit: Fixed code block html tags

Solution 1

You should have noticed from the replies to you other questions.
Only ask your question ONCE.
Cross-posting like this will only annoy those people who might otherwise help you.

Posted 26-Nov-12 19:45pm

Peter_in_2780

Solution 3

Try this

C++

#include <stdio.h>
#include <stdlib.h>
 
int main(void) {
    char again = 'y';
   //...............
}

Posted 26-Nov-12 21:50pm

Snk Tay

Updated 27-Nov-12 12:58pm

v2

Comments

ho_khalaf 27-Nov-12 15:41pm

your code is good but when i use it like this did not work.
#include <stdio.h>
#include <stdlib.h>

void scan_frac(int *num,int *denom);

int main(void){
int num1,denom1;
char again;
do{
scan_frac(&num1,&denom1);
printf("insert (y)to do another problem");
fflush(stdout);
again=getchar();
getchar();
}while(again=='y'||again=='Y');

return 0;
}

Albert Holguin 27-Nov-12 18:59pm

Edit: Fixed code block html tags

Solution 5

I dont know how correct is that write below!!
But when you scan a char as a string it works!!

C++

#include <stdio.h>
#include <stdlib.h>

int main()
{
      char c;
      do
      {
            printf("Give y or Y to loop again: ");
            scanf("%s", &c);
            fflush(stdout);
      }while(c == 'y' || c == 'Y');
}

If do while loot not works again just try the while loop

C++

int main()
{
       char c = 'y';
       while(c == 'y' || c == 'Y')
       {
            printf("Give y or Y to loop again: ");
            scanf("%c", &c);
            fflush(stdout);
       }
}

Posted 27-Nov-12 12:22pm

Snk Tay

Updated 27-Nov-12 12:59pm

v2

Comments

Albert Holguin 27-Nov-12 19:00pm

Edit: Fixed code block html tags

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CPallini · Accepted Answer · 2012-11-26T22:31:00

Solution 4

I works. But it doesn't work the way you think it does.
As a simple workaround you may use a string instead of char as input for scanf, e.g.

C

#include <stdio.h>
#include <stdlib.h>

int main(void) {
    char buf[0x100];
    do{
        printf("insert y or Y to repeat");
        fflush(stdout);
        while (scanf("%s",buf) != 1);
    }while(buf[0]=='y'|| buf[0]=='Y');
}

[Update]
try this one:

C

#include <stdio.h>
#include <stdlib.h>
int scan_frac(int *num,int *denom);

int main(void){
  int num1,denom1;
  char buf[0x100];
  do{
    if ( scan_frac(&num1,&denom1) == 2)
    {
      if ( denom1 != 0)
      {
        printf("%d/%d = %g\n", num1, denom1, ((double)num1)/denom1);
        fflush(stdout);
      }
    }

    printf("insert (y) to do another division\n");
    fflush(stdout);
    scanf("%s", buf);
  }while(buf[0]=='y'||buf[0]=='Y');

  return 0;
}
int scan_frac(int *num,int *denom){
  int values;
  int n,dn;
  printf("insert numerator and denominator (use blank as separator): ");
  fflush(stdout);
  values = scanf("%d %d",&n,&dn);
  *num=n;
  *denom=dn;
  return values;
}

[/Update]

Posted 26-Nov-12 22:31pm

CPallini

Updated 27-Nov-12 11:13am

v2

Comments

ho_khalaf 27-Nov-12 15:40pm

your code is good but when i use it like this did not work.
#include <stdio.h>
#include <stdlib.h>

void scan_frac(int *num,int *denom);

int main(void){
int num1,denom1;
char again;
do{
scan_frac(&num1,&denom1);
printf("insert (y)to do another problem");
fflush(stdout);
again=getchar();
getchar();
}while(again=='y'||again=='Y');

return 0;
}

ho_khalaf 27-Nov-12 17:34pm

thank you very much.i test your solution and worked good.
you are good programer in c\c++ programing.

CPallini 27-Nov-12 17:45pm

You are welcome.
Thanks for your appreciation.

[no name] 27-Nov-12 19:21pm

my English is only the begining,but you program is much better than me.

CPallini 28-Nov-12 3:46am

It is only experience, both your English and your programming skills will be soon better.

Albert Holguin 27-Nov-12 19:05pm

Does he really understand why his code doesn't work?

ho_khalaf 28-Nov-12 9:14am

Yes i understand.I use a "string" instead of "char" as input for "scanf".

Albert Holguin 28-Nov-12 10:11am

Why?

ho_khalaf 28-Nov-12 10:24am

because of compiler bug.when use char in scanf("%c",a) in big program scanf read hole line and it dose not read just a character.

[no name] 29-Nov-12 1:20am

scanf("%s",buff),scanf("%c",buff),you should know the difference of %s and %c