Random number + guessing game trouble

I've been trying to work on my first program for the last 5 hours, this program should be very simple but even so I've had countless different problems with it )=

The program idea comes from a book called Teach yourself C, second edition, 1994 pg. 57. The problem is stated as so (I'm going to shorten it some and put it into my own words):

Create a program that generates a random number, allow it so a user has 10 chances to guess the said random number. The value of the generated number should be within 1 and 100. When a player makes a guess inform the user if his guess is to low or to high.

Unfortunately the book doesn't show to create a random number (at least up to this point it hasn't), because of this I had to look up a function that could (I'm going to try to use rand() )

So far I've encountered the following problems:

• For some reason, my compiler likes to compile things from the trash bin (things with the same name as my file i want to compile). This little problem took me quite some time to figure out, I would edit the program and i would get the same messages as before. So no one encounters this problem, when you delete a file say named guess.c and decide to make a new file (same name) close your editor and reopen it. I don't know why that works but it allowed me to actually try to compile the program I wanted to. Also emptying trash bin will work. If anyone has experienced this and knows why please tell me.
  
  
• The second problem I had was I didn't include the right .h files. This one took even longer to figure out and seems kinda a silly mistake.
  
• My next problem is the one I'm stuck on, I have edited and fixed and edited some more, but my program will not run (ok thats not true it does, but it won't do what I want it to). I need to generate a random number, which I have tried to do (as shown in the following code), I set it so the rand() function gets a random number, then my program is supposed to modify it so the new number is between 1 and 100. As my program runs I have found no matter what number I run I get the returned message I need to guess even higher, even when I guess higher than the limit I have set (or apparently though I set).
  
• My last problem is my program seems to go a little crazy when I try to put a character instead of an integer into the input )= I would think setting the variable to an int type would stop that problem.

So now here is my program, unfortunately its not what I really wanted I tried to add all the loop functions but I changed it thinking it was wrong before do to the first problem I had )= So now all it has is boring if loops. Also I have heard that goto function is very bad, well I'm not sure what I can use in its place so I had to use it (=

Code:

---

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

int main(void)
{

int guess, try, correct;
int max;
int low;

try = 10;
max = 100;
low = 1;
correct = rand();

/* this will attempt to give a random value to the variable "correct" */

 
repeate:
       
        if (correct < 0)
        {
        correct = -correct;
        }

        if (correct > max)
        {
        correct = correct/2;
        }
       
        if (correct < low)
        {
        correct = correct * 2;
        }
       
        if (correct < 1)
        {
goto repeate;
        }

        if (correct > 100)
        {
goto repeate;
        }

/* This asks a user to guess a number as long as their trys have not been used up */

while (try != 0)

{

        printf("Guess a number from 1-100, you have %d tries\n", try);
        scanf("%d", guess);

        if (guess == correct)
        {
                printf("Correct, good job\n");
                try = 0;
        }

        else if (guess > correct && try != 0)
        {
                printf("Sorry try agian, this time guess lower\n");
                try = try - 1;
        }

        else if (guess < correct && try != 0)
        {
                printf("Wrong, Try again. This time guess higher\n");
                try = try - 1;
        }
       
       

                if (try == 0 && guess != correct)
       
                        printf("You lose\n");
       


}
return 0;
}

---

I'm shure theres some basic reason I can't get it to work... But I have missed it up to this point. Also if it helps I am running linux, and the compiler I use is gcc.

thanks to anyone that can help (or took the time to read any of that) (=

Wow, well goto's and labels aren't really recommended anymore. Also try and use indenting...

I would try a re-write, plan from the start

Sorry about the layout of the program. I will do a rewrite but first do you see anything that would result in the program not working? At this time I'm using gotos because I lack the knowledge of using anything else )=
Also may I ask why people have stopped using the goto function?

Because it's confusing & hard to read, loops and ifs are better.

If you want a number between 1 and 100, use:

Code:

---

int num = rand() % 100 + 1;

---

you have a broken logic

rand never returns negative numbers
if (correct < low) - in your case it means 0
0*2 and 0/2 is still 0

to get a random value in the [low,high] regeon you can use for the start the simple approach
correct = low + rand()&#37;(high-low+1);

Quote:

---

Originally Posted by vart

you have a broken logic

rand never returns negative numbers
if (correct < low) - in your case it means 0
0*2 and 0/2 is still 0

to get a random value in the [low,high] regeon you can use for the start the simple approach
correct = low + rand()%(high-low+1);

---

Okay simpilar is better (= But I guess I am misunderstanding how

Code:

---

if (correct < low)

---

would be the resulting of the error, if rand will never give me a negative number than wouldn't the program just pass over:

Code:

---

if (correct < 0)
        {
        correct = -correct;
        }

---

And procede to the following if statements?

I see now that if rand happened to give back 0 then in that special case the program should fail, but wouldn't at all other times it run fine?

Quote:

---

in that special case the program should fail, but wouldn't at all other times it run fine?

---

I said your logic is broken one place... I haven't checked if it is OK all other places...

Use debugger to see what happening...
Or add temporary printfs to trace your program

Quote:

---

Originally Posted by vart

I said your logic is broken one place... I haven't checked if it is OK all other places...

Use debugger to see what happening...
Or add temporary printfs to trace your program

---

Ok thats a good idea, thanks for your response.

Look at the following code:

Code:

---

        if (correct < low)
        {
        correct = correct * 2;
        }

---

As you can see, you defined low as being 1, so any number inferior to low is definitely smaller than 1. This in turn, is a decimal number anywhere between 0 and 1. Let's take 0.5 as example:

0.5 * 2 = 0.25

So your multiplication doesn't help one bit but results in an infinite loop. Since you're using integers anyway, anything below 1 will be truncated to 0. So you're ending up in an endless loop, multiplying 0 all the time by 2.

0.5 * 2 = 1

Quote:

---

Originally Posted by KONI

0.5 * 2 = 0.25

---

Shouldn't that be "0.5 * 2 = 1" instead? You're dividing in this case. Integer division can cause unforseen problems that you wouldn't normally expect. 9/5 isn't 1.8 or 2 in the case of integer division, it's 1. The trash after the decimal is ignored/discarded.

I don't understand the repeate and goto things (is that even C?) so I can't help you there.

Quote:

---

Originally Posted by ulillillia

Shouldn't that be "0.5 * 2 = 1" instead? You're dividing in this case. Integer division can cause unforseen problems that you wouldn't normally expect. 9/5 isn't 1.8 or 2 in the case of integer division, it's 1. The trash after the decimal is ignored/discarded.

I don't understand the repeate and goto things (is that even C?) so I can't help you there.

---

I suppose multiplying anything less than 1 (zero in this case) wouldn't make sense (=
I guess I was thinking that the integers where getting rounded up, but that obviously isn't the case here.

As for the goto function, it is part of the C language (according to my book... My old book). from what I have been told it is now not used very often. The only reason I use it is because I have found it easier to deal with then the normal loops and I don't have a better way of doing things at this time (=.



By the way I have got my program to tell me if I'm higher or lower when I guess a number, but for some reason rand() has only been giving me the number 53 every time )=

Quote:

---

By the way I have got my program to tell me if I'm higher or lower when I guess a number, but for some reason rand() has only been giving me the number 53 every time )=

---

read srand description

Thank you this looks like exactly what I needed (=

Code:

---

while (value < another)
{
        // do stuff
        value++;
}

---

That's a basic loop. The loop continues until the condition is false (or a "break;" is added). There's also for and do-while. I mostly prefer "while", but there are cases where "for" comes in handy. Leaving out the "value++;" item will cause an infinite loop which makes closing the program a pain (not in Windows 98 though, but in XP Pro it is).

For fractional values, use floats or doubles (but be careful when using high precision - 7.000000001 as a float is actually 7.0, but as a double, it's different). Floats have 7 significant figures and doubles have 15. Using == for conditions will almost always make them false - use ranges and something "close enough" instead.

Quote:

---

Originally Posted by zacs7

0.5 * 2 = 1

---

Not in my own private world where everyone is naked and I am king of the universe.

Damn, what a shameful post ...

Nevermind, I also have a parallel universe where everyone is also naked. :)

We also make silly math mistakes too :P