Graal Forums - Variable argument count?

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Loriel

02-06-2009 01:11 AM

Variable argument count?

How do I pass all or some of my however many arguments to another function taking a variable amount of arguments?

As in lua's function foo(x, y, ...) something_with(x, y) bar(...) end, I guess.

Crow	02-06-2009 01:14 AM

Uhhh...could probably use the params[] array.

Loriel

02-06-2009 01:24 AM

Quote:

Originally Posted by Crow (Post 1463354)

Uhhh...could probably use the params[] array.

How do I use the params array?

Crow	02-06-2009 01:57 AM

Quote:

Originally Posted by Loriel (Post 1463359)

How do I use the params array?

Well, it's an array that stores the arguments. Example:

PHP Code:


		
			
function myFunc(arg1, arg2, arg3) {

  echo(params[0]);

  echo(params[1]);

  echo(params[2]);

}

Would echo arg1, arg2 and arg3 in that order. So you could probably check the size of that array, do some magic, and then pass the arguments to another function.

Loriel

02-06-2009 02:11 AM

Quote:

Originally Posted by Crow (Post 1463377)

Would echo arg1, arg2 and arg3 in that order. So you could probably check the size of that array, do some magic, and then pass the arguments to another function.

Could you elaborate on the magic?

Edit: Uh, how do I even call that function to make params[0] actually hold a value?

Crow	02-06-2009 02:13 AM

Quote:

Originally Posted by Loriel (Post 1463389)

Could you elaborate on the magic?

No idea what one could do in this case. Though, since this is still Graal, using that array is probably the only way to go. I don't have an idea how exactly you could do this though.

Programmer

02-06-2009 02:38 AM

Quote:

Originally Posted by Loriel (Post 1463389)

Could you elaborate on the magic?

Edit: Uh, how do I even call that function to make params[0] actually hold a value?

params[] is set to the total sum of the variables passed into a function. Consider the following:

PHP Code:


		
			
function Foo(bar, baz)

{ ... }



Foo(1, 2, true, 999);

bar would equal 1, and baz would equal 2. However, the params array looks like this:

PHP Code:


		
			
{1, 2, true, 999}

And thus, the above function can literally be transcribed into:

PHP Code:


		
			
function Foo()

{

    bar = params[0];

    baz = params[1];

}

This is not dissimilar to C#'s implementation of parameters, if you're into that:

PHP Code:


		
			
// C#

private void Foo(params object[] parameters)

{

     var bar = parameters[0];

     var baz = parameters[1];

}

Loriel

02-06-2009 02:45 AM

Quote:

Originally Posted by Programmer (Post 1463404)

params[] is set to the total sum of the variables passed into a function. Consider the following:

PHP Code:


		
			
function Foo(bar, baz)

{ ... }



Foo(1, 2, true, 999);

I cannot quite get this to work. I inserted echoo({bar, baz}); into the function body for testing. Indeed it outputs 1,2 as I expected.

Quote:

And thus, the above function can literally be transcribed into:

PHP Code:


		
			
function Foo()

{

    bar = params[0];

    baz = params[1];

}

Now when I do this, the output is "",0. If I say echo(params), I do not get any output at all. Am I missing something here?

Quote:

This is not dissimilar to C#'s implementation of parameters, if you're into that:

PHP Code:


		
			
// C#

private void Foo(params object[] parameters)

{

     var bar = parameters[0];

     var baz = parameters[1];

}

I think it is indeed dissimilar, because I could call that function with a single array instead of a list of parameters.

Programmer

02-06-2009 04:04 AM

Quote:

Originally Posted by Loriel (Post 1463407)

I cannot quite get this to work. I inserted echoo({bar, baz}); into the function body for testing. Indeed it outputs 1,2 as I expected.

Try:

PHP Code:


		
			
function Foo(bar, baz)
{
    echo({ bar, baz });
    echo(params);
}

Foo(1, 2, true, 999);

Will echo:

HTML Code:

1, 2

-- Comment: 'true' is represented as 1.

1, 2, 1, 999

Quote:

Originally Posted by Loriel (Post 1463407)

Now when I do this, the output is "",0. If I say echo(params), I do not get any output at all. Am I missing something here?

0 in Graal is literally translated as 'null', and will print absolutely nothing to the RC. An empty string literal will obviously print nothing as well.

Quote:

Originally Posted by Loriel (Post 1463407)

I think it is indeed dissimilar, because I could call that function with a single array instead of a list of parameters.

In C#, it's similar in this manner:

PHP Code:


		
			
// C#
private void Foo(params object[] parameters)
{
     var bar = parameters[0];
     var baz = parameters[1];
     
     Console.WriteLine("Result: " + bar + ", " + baz);
}

Foo(1, 2);

// OUTPUT:
// Result: 1, 2

cbk1994

02-06-2009 04:42 AM

I've had some problems where the params[] array is erased/non-existent if you assign variables to the parameters in the function.

Admins

02-06-2009 04:52 PM

The params[] array is only created when the script is called (doesn't even need to be a function, GS1 style). That is either on an event, or when you call a function of another object. To get a variable number of parameters either use func(arg1, arg2, arg3, arg4 etc) and ignore the arguments that you don't want, or pass the parameters as array.

Currently accessing the parameters for each function as array is not possible because it would mean a big speed slowdown, although if it's really important to have it then we could add something like temp.functionparams[] which dynamically converts the function parameters to variables.

Loriel

02-06-2009 05:36 PM

Quote:

Originally Posted by Stefan (Post 1463493)

Thanks, that clears it up. Some experimentation suggested the FAQ thread was inaccurate about this and some dude on IRC said it only worked for triggers, so that makes sense.

Quote:

Currently accessing the parameters for each function as array is not possible because it would mean a big speed slowdown, although if it's really important to have it then we could add something like temp.functionparams[] which dynamically converts the function parameters to variables.

Not important, I really just wanted to build an error reporting function that would forward all its arguments to format() and print the resulting string with more error stuff, instead of having the user call format, and consequently got confused about how variadic functions even work.

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