CODEWITHSUNDEEP
c
J.Leo
J.Leo

Reputation: 13

C program stops after first the first recursive call

I've tried to use character data type to compare in variable reply if equal to y it will continue calling the function recursion(), however, it did only 1 recursion() call and the program terminated. This only work if I use the int data type, as the variable to compare. Please anyone can let me know why this happen?

#include <stdio.h>

void recursion()
{
    char reply;
    printf("Continue?:");
    reply=getchar();
    if(reply=='y')
    {
        printf("Continued\n");
        recursion();
    }
}

int main()
{
    recursion();
    return(0);
}

output:

Laptop1:User1$ ./recur 
Continue?:y
Continued
Continue?:Laptop1:User1$

Upvotes: 1

Views: 161

Answers (2)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 727137

The problem is that when end-users enter 'y' in the terminal, they press Enter. This inserts another character into the stream - '\n'. That is the character that the next call to getchar() would return, ending the chain of calls due to

if(reply=='y')

condition evaluating to "false".

You can fix the problem in several ways - for example, by using scanf:

if (scanf(" %c", &reply) == 1 && reply == 'y')
//         ^
// Note the space above

Adding a space character in front of %c ensures that scanf skips whitespace characters before reading the character into reply variable.

Upvotes: 0

MikeCAT
MikeCAT

Reputation: 75062

getchar() will read newline character if it is, and it will prevent it from continueing.

Try this:

#include <stdio.h>

int getchar2()
{
    int c;
    do
    {
        c = getchar();
    } while (c == '\n'); /* ignore newline characters */
    return c;
}

void recursion()
{
    int reply;
    printf("Continue?:");
    reply=getchar2();
    if(reply=='y')
    {
        printf("Continued\n");
        recursion();
    }
}

int main()
{
    recursion();
    return(0);
}

Upvotes: 3

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