Thread: Declare varialbe only once?

Hello, I am in a begging programing class and I am having trouble with my program. It is a craps game. I have to give the player $100 to start with and then they lose money as they go. The issue i have is... I set chips = 100 at the beginning of the program, but then later on they get chips added or taken away. So is it possible to just declare it once? Any information will help. Thanks, Curtis.

Yes, it's possible, and kinda necessary to only declare it once. Once you declare a variable, you can use it as many times as you want (to read the value, set the value, use it in an expression, etc...) as long as it's in scope. If you declare it inside a function, it's scope ends when the function ends. If you make it global, you can use it in any function. Alternately, you could declare it one function, then pass it as a parameter to other functions that need it, etc... Remember that if you declare the variable in one function to remember how many chips the player has, if a different function declares a variable in a different scope (even with the same name) it's a completely different variable - and you won't be able to track how many chips the player has.

As mentioned, it really only makes sense to declare a variable once. Note that "declare" is certainly not the same as "assigning" or "changing" the value of a variable. If you want to prevent the value of a variable from changing, i.e. for it to be "constant", then declare it as such

Code:

const int answerToLife = 42;

So that the value of this cannot be changed (and is a compiler error if you try to change it). Going back to declaring a variable only once, if you're a math guy/girl, then the following scenario should be obviously incorrect

Code:

Suppose we are graphing the relationship between these variables. Let X be the number of hours I spend practising programming.
Let Y be the grade I get in the course.
Let X be the number of hours I spend sleeping.

Again, it doesn't make sense to declare "X" again.

I understand all that. What I need is a way that, once the loop finishes it sets the chips back to 100 so is there a way to only have it set to 100 for the first time around? and thank you for the replies

So you're game is inside a loop, so that the person can "play again" or "exit", etc? If so, then can't you just assign the value at the beginning of the loop?

Code:

char playAgain;
// ...
do
{
// set number of chips here at start of game

// rest of your game code
} while ( playAgain == 'y');

Assuming you ask the user to "play again", etc.

yes its in a loop here is what ive got.... i just need to figure out a way to where chips=100 isnt valid after the first time through the loop.

insert

Code:

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

int main(void){
double bet, chips, final;
int roll, roll1, status, point, i;

chips=100;
chips=final;

printf("* Welcome to my casino. The game this evening *\n");
printf("* is Craps. (Pass line bets only, but what do *\n");
printf("* you want from a class project?) *\n");
printf("* The minumum bet this evening is $2.00\n");

while(final>2) {

printf("You have $%.2f.\n", final);
printf("How much would you like to bet?");
scanf("%lf", &bet);
printf("\n");

if(bet>0 && bet<2) {
printf("I'm sorry, you can only bet between $2.00");
printf("and $%.2f (or 0 to quit).\n", final);
}

if(bet==0) {
printf("Your final bankroll is $%.2f.\n", final);
printf("Looks like you had a good night.\n");
printf("See the cashier on your way out.\n");
return 0;
}

srand(time(NULL));
roll= rollone(12);
printf("Coming out...%d\n", roll);
printf("Your point is %d\n", roll);

switch(roll) {

case 7:
case 11:
printf("A pass. We have a winner.\n");
printf("You win $%.2f\n", bet);
status=1;
break;

case 2:
case 3:
case 12:
printf("Craps.");
printf("You lose $%.2f.\n", bet);
status=2;
break;

default:
status=0;
point=roll;
break;
}

while(status==0) {
srand(time(NULL));
roll1=rollone(12);
printf("Coming out...%d\n", roll1);
printf("Your point is %d\n", roll1);
if(roll1==point) {
status=1;
}

else {
if(roll==7 || roll==11)
status=2;
}
}

if(status==1) {
printf("You win $%.2f\n", bet);
final=chips+bet;
}
if(status==2) {
final=chips-bet;
}
}

if(final==0) {
printf("I’m sorry. You can’t afford another bet.\n");
printf("Your final bankroll is $%.2f./n", final);
printf("Better luck next time.");

}

return 0;
}

Its quite difficult to read the code if its not indented. In the future, make sure it is indented when you post any code.

I still think you can just put your code inside an outer loop, like I described above. So that you have an outer loop (the one I described above) which loops the entire game, so that they can play again, the variables and chips can get reset, etc.. Then inside you have your game. It just so happens that your game has a loop in it, too. After they loose, you can ask them if they want to play again, etc..

Is this even what you're talking about? That is, you want to reset the money and other things because you want them to be able to play again?

Others will probably point out the actual errors in your code, such as the fact that you are using variables without giving them a value. For example, you declare (again, this does not mean assigning a value) "final", and then you use it in the "while" loop condition ("final > 2"). You must make sure to assign values to all variables before using them. If you're compiling with a verbose warnings option, then you'll see the compiler complaining about doing this. Let's suppose your applying for a job and you ask how much the hourly wage is. They tell you its X dollars. What is X? Maybe its 40, and so a great wage, on the other hand maybe its 5--who knows. This is the same with what you're currently doing in the program when you use variables without assigning them values.

Also,

Code:

chips=100;
chips=final;

You assign "chips" the value of 100. Then right after that you overwrite the value of chips, and reassign it the value of whatever "final" is (as stated above, no one knows what "final" contains!). This probably isn't what you want to do.

I dont know how to play Craps, so I can't help with the actual logic.

Yeah there are specific guidelines i have to follow for class that are the player continues to play until they have <$2 or out by betting $0

Originally Posted by sean

Yes, it's possible, and kinda necessary to only declare it once. Once you declare a variable, you can use it as many times as you want (to read the value, set the value, use it in an expression, etc...) as long as it's in scope. If you declare it inside a function, it's scope ends when the function ends. If you make it global, you can use it in any function. Alternately, you could declare it one function, then pass it as a parameter to other functions that need it, etc... Remember that if you declare the variable in one function to remember how many chips the player has, if a different function declares a variable in a different scope (even with the same name) it's a completely different variable - and you won't be able to track how many chips the player has.

A few corrections

If you declare it inside a function, it's scope ends when the function ends.

This is only true if the variable inside the function isn't static.

If you make it global, you can use it in any function.

This is only true if the variable has external linkage.

Okay, maybe you can clarify some possible misconceptions that I have here..

Let's say that I have variable 'a' with static duration inside a function block. According to ISO/ANSI c88(?), the variable 'a' is just basically a named object. So with that, wouldn't the value of the object remain the same after the function leaves the block? Ie, the variable 'a' itself would cease to exist after the function gets done executing.