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Multiple local variable passing, questions.

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Belthemet

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Multiple local variable passing, questions.

Aug 14th, 2009

Hello.

Currently I'm making a game in C++, its not my first game (Examples of what I've made is "The game of life" in both 3d and 2d, TicTacToe with my own AI algorithms (based on the graph theory), 2D Paratrooper game), however its my first programm that requires allot of parameters to be passed from function to function.
I'm quite familiar with the structured part of C++ and some other languages, however I'm not quite advanced in the object oriented\class part of the C++ language, so this might be my problem.

First thing I would like to say, I do not want to use global parameters, unless they are global constants. In my experience they ruin the code and ruin the concept of structured programming.

Usually If passing certain parameters would be required, I would just pass them by reference:

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void foo(int &myvar); {}
void foo(int &myvar); {}

But in this case I'm making an RPG game with a huge amount of variables, so I would have to do:

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void foo(int &myvar, int &myvar2, ...., int &myvarN); {}
void foo(int &myvar, int &myvar2, ...., int &myvarN); {}

Sometimes, I would need to pass only one or two variables, but I can't just leave all the other variables blank.

So, I assume the best way to solve this problem is using classes, however I couldn't figure out a good way to do so. If you could share some ideas or show some examples that would be great.

Here is a more precise example:

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void data() {
param1 = ...
param2 = ...
param3 = ...
....
paramN = ...
 
result1 = param1+param2*param3
result2 = param3*param1+param2
....
resultN = paramN-paramA+paramB
}
 
void func1(); {
 
if(foo == foo2) {
data();   <span class="ad_notxt"><code class="inlinecode">/* How would I pass param1, param2 but not pass any other params? Lets say data() would be data(int a, int b, int c) its impossible to just pass a, b and not c ?*/</code></span> }
 
int main() {
func1();
data();
return 0;
}
void data() {
param1 = ...
param2 = ...
param3 = ...
....
paramN = ...

result1 = param1+param2*param3
result2 = param3*param1+param2
....
resultN = paramN-paramA+paramB
}

void func1(); {

if(foo == foo2) {
data();   <span class="ad_notxt"><code class="inlinecode">/* How would I pass param1, param2 but not pass any other params? Lets say data() would be data(int a, int b, int c) its impossible to just pass a, b and not c ?*/</code></span> }

int main() {
func1();
data();
return 0;
}

Last edited by Belthemet; Aug 14th, 2009 at 12:58 pm.

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Re: Multiple local variable passing, questions.

Aug 14th, 2009

You can use functions with the variable number of parameters.
Example of that function is a printf() function.
It define how much parameters he have by calculating '%' symbols in the first parameter.

Examples:
MSDN
http://www.codersource.net/c++_varia...functions.html
Just information

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Re: Multiple local variable passing, questions.

Aug 14th, 2009

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its impossible to just pass a, b and not c ?*/

Not necessaryly.

Well another alternative would be to give default values to your arguments for eg:

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void funcname(int a, int b=0, int c=0);
void funcname(int a, int b=0, int c=0);

Now i can just call the function in these 3 manners for eg:

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int val1=10, val2=20,val3=30;
 
funcname(val1);//Only one variable.
funcname (val1,val2); //THis will consider that the 3 variable is default.
funcname (val1,val2,val3); //All values given in.
int val1=10, val2=20,val3=30;

funcname(val1);//Only one variable.
funcname (val1,val2); //THis will consider that the 3 variable is default.
funcname (val1,val2,val3); //All values given in.

The only problem would be that you are not allowed to call like the code below

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funcname(val1,, val3)//this would be an errror
funcname(val1,, val3)//this would be an errror

I hope this helps you out.

Last edited by Sky Diploma; Aug 14th, 2009 at 1:29 pm. Reason: Added quotes.

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Belthemet

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Re: Multiple local variable passing, questions.

Aug 14th, 2009

Thank's for the info Protuberance and Sky Diploma. I will try these methods and see if I run into any more problems.

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Re: Multiple local variable passing, questions.

Aug 14th, 2009

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Originally Posted by Sky Diploma

The only problem would be that you are not allowed to call like the code below

This error is not undecidable

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funcname(val1, 0, val3);//no error
funcname(val1, 0, val3);//no error

Another solution of this problem is using array.
You can allocate memory for temporary array and pass it to the function. Since that function will return some result, just free memory which allocated for an array.
That method is not very good. But it's effective. And don't forget to free allocated memory, because you can get the memory-leak.

P.S. for array method - you have to pass a size of array into the function. Because otherwise you can get OutOfRangeException.

P.P.S. If you will use std::vector or something similar from STL, there is no need to pass size of array. You can define size into the function.

Last edited by Protuberance; Aug 14th, 2009 at 3:03 pm.

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Re: Multiple local variable passing, questions.

Aug 14th, 2009

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This error is not undecidable

That was just an attempt to show that there is an exception to default arguments..

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Re: Multiple local variable passing, questions.

Aug 14th, 2009

Go for class structure. It will definitely be a lot easier and less work,
as well as more elegant.

Here are some ideas :

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class Hero{};
class BigHeadMonster { };
class Items { };
class Story { };
Class Map { };
class Hero{};
class BigHeadMonster { };
class Items { };
class Story { };
Class Map { };

Pick a class, start implementing it, and go from there.

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Re: Multiple local variable passing, questions.

Aug 15th, 2009

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Originally Posted by Protuberance

Another solution of this problem is using array.

Thanks, this seems to be the best method so far.

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Originally Posted by firstPerson

Go for class structure. It will definitely be a lot easier and less work, as well as more elegant.

Thank's for the reply firstPerson, I have mentioned that I havent fully explored the class and OOP potential of C++. Could you show some examples/tutorials on using classes? So far I don't see a big difference between a class and a function

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Re: Multiple local variable passing, questions.

Aug 15th, 2009

"so far I don't see a big difference between a class and a function "

WOW. Read Me

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1) What word becomes shorter if you add a letter to it? [ Solved by : niek_e, Paul Thompson]
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