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Functions with a variable number of parameters using (...)

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Submitted on: 1/2/2015 4:11:00 AM
By: Derick Dong (from psc cd)  
Level: Intermediate
User Rating: By 3 Users
Compatibility: C++ (general), Microsoft Visual C++
Views: 1016
 
     To demonstrate how to create a function with a variable number of parameters, similar to the printf function. *Just fixed this, so now you can actually read it.

 
				
Somebody asks me how to do something like this,
so I'm posting it. Basically, its a function like
printf, that can take a variable number of
arguments, using the (...). I use something like
this to create a string for my graphics programs,
and draw the resulting string to the screen.

// Create a string function
void CreateAString(const char *format, ...)
{
va_list list;
char string[1024];

// Create the string from the parameters
va_start(list, format);
vsprintf((char *)string, format, list);
va_end(list);

// Function to draw the string goes here
}

Now, the complete string is stored in 'string'.
To use this function, you can use something like:

void function()
{
int num1 = 10, num2 = 20;
CreateAString("NUM1 = %d NUM2 = %d", num1, num2);
}

And 'string' would be:

NUM1 = 10 NUM2 = 20

Pretty easy. Not used real often, but it can be useful.


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