Passing arrays to functions

Array are just like any other variables in that they can be passed into functions as parameters. Here's a small example program that shows how it is done.

score as integer [ 3 ]


score [ 1 ] = 10
score [ 2 ] = 20
score [ 3 ] = 30


do
	UpdateScore ( score )
	

	for i = 1 to 3
		print ( score [ i ] )
	next i
	

	sync ( )
loop


function UpdateScore ( values as integer [ ] )
	for i = 1 to values.length
		values [ i ] = values [ i ] + 2
	next i
endfunction

Here's how it works.

• An array named score is declared. It has a size of 3.
• Each part of the score array is given a value.
• A function named UpdateScore is called passing in the variable score.
• The do loop prints out the contents of the variable score.
• The function UpdateScore has declared the type of parameter as being integer and added an opening and closing bracket, signalling to the program that an array is expected to be passed into this function.

If you run this program you will see 0, 0 and 0 displayed on screen instead of the scores continually getting larger and larger as you might expect. The reason for this is that by default AppGameKit takes parameters being passed into functions and copies their data, resulting in the parameter being a complete copy of the data passed in. The original data remains untouched by the function.

If you want to modify the data being passed into the function then the parameter needs to be declared slightly differently - use the ref keyword after the name of the variable and before the as keyword. Here's the same program, but this time the type is passed in as reference, resulting in its data being modified directly by the function.

score as integer [ 3 ]


score [ 1 ] = 10
score [ 2 ] = 20
score [ 3 ] = 30


do
	UpdateScore ( score )
	

	for i = 1 to 3
		print ( score [ i ] )
	next i
	

	sync ( )
loop


function UpdateScore ( values ref as integer [ ] )
	for i = 1 to values.length
		values [ i ] = values [ i ] + 1
	next i
endfunction

When you run this program all 3 scores contained within the array will continually increment because the parameter has been declared using ref, therefore a copy is not made and the data being passed into the function will be directly modified by the function.

To pass multidimensional arrays to functions use additional square brackets in the function declaration, as shown in this program.

score as integer [ 2, 3 ]


score [ 1, 1 ] = 10
score [ 1, 2 ] = 20
score [ 1, 3 ] = 30


score [ 2, 1 ] = 100
score [ 2, 2 ] = 200
score [ 2, 3 ] = 300


do
	UpdateScore ( score )
	

	for i = 1 to score.length
		for j = 1 to score [ i ].length
			print ( score [ i, j ] )
		next j
		

		print ( "" )
	next i
	

	sync ( )
loop


function UpdateScore ( values ref as integer [ ] [ ] )
	for i = 1 to values.length
		for j = 1 to values [ i ].length
			values [ i, j ] = values [ i, j ] + 1
		next j
	next i
endfunction

The UpdateScore function has two sets of brackets for the parameter, meaning it expects a 2 dimensional array to be passed into it. If three sets of brackets were to be used then a 3 dimensional array would need to be passed into the function.