Thread: Newbie need some help

I have some problem with my program, it won't run into the

Code:

if (selection2=='y'){
            system("clr");
            return main();
         }

please help me with this

Code:

#include<stdio.h>
#include<stdlib.h>
int main(){
    float km,ml,result;
    int selection;
    char selection2;
    
    printf("\n\nPlease select the mesurement unit you want to convert with\n");
    printf("1) Kilometer\n2) Mile\n");
    scanf("%d",&selection);
    if (selection==1){
        printf("\nPlease enter the kilometers \n");
        scanf("%f",&km);
        result=km*0.621371;
        printf("\n %.2f km = %.2f mile",km,result);
    }
    else if (selection==2){
        printf("\nPlease enter the miles \n");
        scanf("%f",&ml);
        result=ml/0.621371;
        printf("\n %.2f mile = %.2f km",ml,result);
    }
    
    else if(selection!=1 && selection!=2){
        printf("Error, Do you want to restart the program (y/n)");
        scanf("%c",&selection2);
    if (selection2=='y'){
            system("clr");
            return main();
         }
         else
         return 0;
     }
     getchar();
     return 0;
     }

Code:

    if (selection2=='y'){
            system("clr");
            return main();
         }

For starters, NEVER call main() within your code!!!

main() should only be called once by the startup code. You will want to create another function, and call that multiple times if needed.

You should also check the return value from scanf() to insure you have received legitimate data. If not, then you need to clear the input buffer.

Code:

while ((ch = getchar()) != '\n' && ch != EOF);

Don't use "Magic Numbers" in your code. "0.621371", for example. Use a #define with a descriptive name where you need this value.

I'm sure there are more issues, but it is late, and I have not compiled the program. Start with these and repost the code.

Originally Posted by spdragon

I have some problem with my program, it won't run into the

Code:

if (selection2=='y'){
            system("clr");
            return main();
         }

please help me with this

When you read characters you need to clear the input buffer from left over characters of previous read operations to make sure that what you read is the users input change your code to

Code:

else if(selection!=1 && selection!=2){        printf("Error, Do you want to restart the program (y/n)");
        fflush(stdin);  //clear the input buffer from the left over line end characters.
        scanf("%c",&selection2);

    if (selection2=='y'){

            system("clr");

            return main();

         }

         else

         return 0;

     }

Originally Posted by Salem

> fflush(stdin); //clear the input buffer from the left over line end characters.
Right idea, wrong solution.
FAQ > Why fflush(stdin) is wrong - Cprogramming.com

thank you for the input. I read everything there is to read on the provided link and there is a logic behind the post, one that I'm inclined to respect at this point, but after spending some time evaluating the different solution presented there I have to admit that I dislike them all. So far only two solutions are acceptable in my book. 1) the fflash, as far as I have tested it on win 7 64, win xp 32bit and win 8.1 32bit it behaves the same way so I'm inclined to use it on windows and 2 use the conio.h and the kbht function to determine if there are more chars in the buffer to read.
In any case thank you for the input it was educating.

Originally Posted by taazz

So far only two solutions are acceptable in my book. 1) the fflash, as far as I have tested it on win 7 64, win xp 32bit and win 8.1 32bit it behaves the same way so I'm inclined to use it on windows and 2 use the conio.h and the kbht function to determine if there are more chars in the buffer to read.

Most of the time you can completely avoid needing fflush(stdin); at all. A combination of fgets + sscanf is often easy and correct, in that it doesn't necessarily leave behind any stray characters.

Originally Posted by taazz

Opinions don't help me learn so I'm going to avoid addressing them in the future.

Every post is fair game. If you say something stupid, you will get called out on it here.

Does it really matter what only you are doing? The thread is about console applications. If you want to talk about GUI programming I guess you should visit Windows Programming, where that is more topical.

Originally Posted by whiteflags

Does it really matter what only you are doing? The thread is about console applications. If you want to talk about GUI programming I guess you should visit Windows Programming, where that is more topical.

It does to me. If you think you can do better then show us the code and stop "talking" about the code. Sorry but this thread is not interesting any more, I'm out. have fun.

Originally Posted by taazz

Sorry but this thread is not interesting any more, I'm out. have fun.

Your reply is the common refrain of the loser.

There's nothing special about you, little boy. We've seen it again and again. You're not the first and you won't be the last. You're demonstrating a common human weakness summed up in the phrase "a little knowledge is a dangerous thing", or the word "sophomore", meaning wise idiot. You just have it worse than most due to your general lack of intelligence.

A little learning is a dangerous thing;
drink deep, or taste not the Pierian spring:
there shallow draughts intoxicate the brain,
and drinking largely sobers us again.
-- Alexander Pope