Error checking for homework

[drogahnus]

Hey guys, I'm new here. I'm taking an intro to C class and just finished an assignment, but I need a little help with error checking. There are 3 checks I need:

1 - People trying to bet or sell more chips than they have
2 - People trying to spend more money than they have
3 - People trying to bet less than one chip

This is my code, it's for a craps game:

http://pastebin.com/m35adcf5b


Any help as to where to place and how to write to error checks would be greatly appreciated!

[tabstop]

Not going to click click click just to see the code.

Basic idea: you've already written what the checks should look like. You should check for errors as soon as feasible (i.e., as soon as they try to place a bet you should check it makes sense).

[drogahnus]

I tried doing this for error check #3, but it won't print the "Invalid..." statement nor go back to the menu. I haven't figured out the other 2 yet.

if(menu == 3)
                  {
                          
                          printf("How many chips do you want to bet?\n");
                          scanf("%d", &bet_chips);

                          do
                          {
                          scanf("%d", &bet_chips);
                          }while(bet_chips < 1);
                          printf("Invalid number of chips!\n");

[tabstop]

Well, look at what you've written: you will _always_ get input twice -- do-while loops are guaranteed to run -- and then once you have gotten valid input, you will then print out that you have an invalid number of chips. And notice that you never prompt for more input -- you'll just get a blinky cursor and your user has to know what to type.

[drogahnus]

I'm confused. So what should the loop look like then?

[tabstop]

1. If you don't want the loop to always run, then you shouldn't use do-while.
2. If you expect someone to give you input, you should provide a prompt so that they know
   
   1. what was wrong
   2. what you're asking them to re-enter
3. There's more ways to be "wrong" then just to be negative -- to get past the gate, the input must be correct; if you check first for negative, then for betting too much, this will happen:
   

   How many chips do you want to bet? -1
   Please enter a positive number of chips!
   How many chips do you want to bet? 1000
   You don't have that many chips!
   How many chips do you want to bet? -1
   Okay.

[Elysia]

I'm confused. So what should the loop look like then?

A loop is merely logic.
So take your logic that you want to do and translate it into code. That's the basic idea.
In case you can't get it right, then do a flowchart first, or pseudo code and translate into real code.

Another thing you might try is translating your current code into pseudo code / flowchart, and you should see why it's wrong.

[slingerland3g]

If your do-while loops sole purpose is to check user input, then you will need an if conditional placed before your do statement.

printf("How many chips do you want to bet?\n");
scanf("%d", &bet_chips);

if (bet_chips < 1 ) 
{
     do
     {
         printf("Invalid number of chips!\n");
         printf("How many chips do you want to bet?\n");
         scanf("%d", &bet_chips);
      }while(bet_chips < 1);
}

I would place more error checking within your do-while though, as Tabstop mentioned.

[Elysia]

We should not need to tell others this kind of thing. This should be worked out by logical thinking!