There's something wrong with my code...

**jane.d** · 05-17-2014

Everytime I type a character, the number 1 appears in the next line. And i just keep getting the message "Wrong! I have more than that." even when I type a number bigger than 1023
Do you know what's wrong. I've spent hours on this.

Code:

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




int main(void)
{
    srand(time(NULL));
    
    int candies = rand() % 1024;
    
    int c;
    
    printf("Guess how many candies I have. I have less than 1024.\nGo on! Type a number!\n");
    
    while(1) 
    {
        c = scanf("%d", &c);
        
        if(c == candies)
        {    
            printf("%d\n", c);
            printf("That's correct! How did you know that?");
            return 0;
        }
            else if(c > candies)
            {
                printf("%d\n", c);
                printf("No. I wish I had that much...\n");
            }
            else if(c < candies)
            {
                printf("%d\n", c);
                printf("Wrong! I have more than that!\n");
            }
    }
}

**Ferii** · 05-17-2014

Where do you record your value for c?
Sure, you have a prompt to take a value for c, but what does it actually do anything?

**Alpo** · 05-17-2014

Code:

c = scanf("%d", &c);

The problem is here (I think). Scanf() is returning the value of successfully copied arguments (1 in this case), while at the (same time? before? ) trying to copy the user input into the variable.

**jane.d** · 05-17-2014

but what exactly should i do? what part of the code should i change? i'm new to this so...

**grumpy** · 05-17-2014

Originally Posted by Alpo

Code:

c = scanf("%d", &c);

The problem is here (I think). Scanf() is returning the value of successfully copied arguments (1 in this case), while at the (same time? before? ) trying to copy the user input into the variable.

I haven't checked closely enough to determine if it is the only problem.

Just to clarify, scanf() potentially modifies c first (processing the %d specifier) and returns a value. That return value is then stored in c, and any value read is lost. There is nothing inside scanf() which would change that order (returning a value follows the attempt to process the %d format). If an error occurs reading, the error is detected before scanf() returns.

Originally Posted by jane.d

but what exactly should i do? what part of the code should i change? i'm new to this so...

Store the value returned by scanf() in a variable other than c. That way you capture both the value read into c (if any), and the return value from scanf() (which, among other things, will separately indicate if a value was successfully read and stored in c).

**Alpo** · 05-17-2014

Originally Posted by jane.d

but what exactly should i do? what part of the code should i change? i'm new to this so...

Sorry, basically you just need to separate checking the return value of scanf (scanf() is a function defined in the stdio.h header, it returns an int) from the variable you are using with scanf() to store into. You could do it like this

Code:

   if(scanf("%d", &c) != 1)
     return 0;

This would evaluate to false if scanf performs propery, skipping the return. Or you could do like grumpy says

Code:

  newvariable = scanf("%d" , &c);

You would then have a variable you could check to see if scanf() stored correctly, newvariable should be 1 in that case.

Or you could just not check the return value (the YOLO approach to programming :P)

Code:

  scanf("%d", &c);

**phantomotap** · 05-17-2014

the YOLO approach to programming

o_O

Gross.

Soma

**Alpo** · 05-17-2014

Originally Posted by phantomotap

o_O

Gross.

Soma

Sorry, I admit to being a whippersnapper and will kindly get off your lawn lol.

**phantomotap** · 05-17-2014

Sorry, I admit to being a whippersnapper and will kindly get off your lawn lol.

O_o

I don't care if you play chicken with an empty trail screaming "YOLO" all the time. So long as your stupid behavior doesn't infringe on the lives of others, your behavior is not my business.

I do care if you give people stupid advice because you are a lazy or incompetent programmer.

Soma

**grumpy** · 05-17-2014

Those who apply the YOLO approach to programming are more likely to die at the hands of fellow developers.

**Alpo** · 05-17-2014

Originally Posted by phantomotap

I do care if you give people stupid advice because you are a lazy or incompetent programmer.

Look at this site's tutorials Functions in C - Cprogramming.com . You may say (correctly) that best practice isn't a democracy and giving another example of bad habit doesn't make what I supplied any more correct, but I did supply correct answers as well, and if the OP was learning from the tutorials he would be doing the worst of my examples. Also saying "you can do it this way" isn't advocating a thing, just admitting it's existence.

Edit: Also, giving the example without the check for return value might have given an important clue and to what "checking the return value" even means. If I kept doing everything at once in my examples it might be harder for a beginner to separate the check from what scanf() is actually doing with the pointer (as was the original problem).

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