Thread: learning switch

Hello programmers!
i am learning switch, and i gave myself a problem to solve. I want the user to enter 4, then, the program will ask him to enter a character. Everytime i enter 4 the program stops and don't go to the other switch. i have tried many forms before i come here. i would like you guys to help me explain my problem and a little bit about using two switch and a switch in another switch. here is the codes. thank you

Code:

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


 int main()
{
    int a;
    char b;
    scanf("%d",&a);
    switch (a) {
        case 1: {
            printf("1\n");
            break;
        }
        case 2:{
            printf("2\n");
            break;
        }
        case 3: {
            printf("3\n");
            break;
        }
        case 4: {
            scanf("%c",&b);
            break;
        }
        switch(b){
        case 'a': {
            printf("a\n");
            break;
        }
        case 'b':{
             printf("b\n");
             break;
        }
        default: {
            printf("haha");
            break;
        }
    }


    default: {
        printf(" lol");
        break;
    }
    }
    return 0;
}

What the manual says about the scanf format, %c:

Matches a sequence of characters whose length is specified by the maximum field width (default 1); the next pointer must be a pointer to char, and there must be enough room for all the characters (no terminating null byte is added). The usual skip of leading white space is suppressed. To skip white space first, use an explicit space in the format.

scanf(3): input format conversion - Linux man page

You may be wondering how this applies to the above program. When you enter a number because scanf("%d", &a); was called, you also type ENTER to give the final version of the input to the program. This ENTER key becomes \n, which is a whitespace character. As you read above, it is not ignored.

i have no idea what you are talking about. And i just went to that link and still didn't get a clue. Care to explain a little bit more in an easy understanding way for a newbie to programming? thank you.

Also, isn't the second switch, "switch(b)" unreachable?

-

megafiddle - I guess so.

endrick, you may need to move your second switch out of your first one.

Originally Posted by WoodSTokk

This is not what endrick wants. If the user type 4, it will scan for a character. The second switch should only be executed, if the user type 4.

I got that. But I was mistaken about the control flow, I have no clue what I have been thinking. You're of course right, the second switch needs to be nested.

Thank you. i saw the problem, but i have to enter 4b or 4a to access the second switch. anyway i found a way to do it. thank you. i will post it here.

You guys are awesome. i am learning C language and i'm happy with the help i get from you guys. Anyway, based on your explanations i found another way to do it even though it is not a professional way of thinking but it works. Again you guys can look at this code and prolly suggest other ways to do it my simple easy way is like this:

Code:

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


 int main()
{
    int a;
    char b,c;
    scanf("%d",&a);
    switch (a) {
        case 1: {
            printf("1\n");
            break;
        }
        case 2:{
            printf("2\n");
            break;
        }
        case 3: {
            printf("3\n");
            break;
        }
        case 4: {
            scanf("%c",&c);
            printf("enter a letter");
            scanf("%c",&b);




        switch(b){
        case 'a': {
            printf("a\n");
            break;
        }
        case 'b':{
             printf("b\n");
             break;
        }
        default: {
            printf("haha");
            break;
        }
        }
        break;
    }




    default: {
        printf(" lol");
        break;
    }
    }
    getch();
    return 0;
}

OMG i didn't see that i'm very sorry. You are a genius. I wonder when i will be able to correct others lol

Also, in your new program, the indentation is a bit messed up. If someone was reading through it quickly, it looks like your switch(b) is by itself, when in reality, it's part of your case 4: statement. Post 7 by WoodSTokk shows how it should properly be indented.