Functions, Subs, and Return

Functions and Subs let you group logic into reusable routines. Return is used to leave a routine, and functions can return a value.

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Function

Function <name>([<parameter>[, <parameter>...]]) [As <typeName>]
    <statements>
End Function

<name> [As <typeName>]

Function Add(x As Integer, y) As Integer
    Return x + y
End Function

The function name is required.
Parentheses are required, even if there are zero parameters.
The return type is optional.
The terminator must be exactly End Function.

Classic type suffixes work here too.

A function name like Add# gives the function a Double return type.
A parameter like name$ is treated as a String parameter.
A parameter like amount% is treated as an Integer parameter.

Function Add#(left%, right!)
    Return left% + right!
End Function

If you use both a suffix and an As type, they must agree.

Sub

Sub <name>([<parameter>[, <parameter>...]])
    <statements>
End Sub

Sub Render()
    Graphics 800, 600
End Sub

The sub name is required.
Parentheses are required, even if there are zero parameters.
The terminator must be exactly End Sub.

Array Reference Parameters

A parameter can accept an array of any rank. Write empty parentheses after the parameter name for a one-dimensional parameter, or include commas for higher-rank arrays.

<name>() [As <typeName>]
<name>(,) [As <typeName>]

values() — one-dimensional array parameter
grid(,) — two-dimensional array parameter
cube(,,) — three-dimensional array parameter

Inside the function or sub body, you can use ArrayLen and index access on the parameter exactly as you would with a regular array variable.

Function Sum(values() As Integer) As Integer
    Dim total As Integer
    Dim i As Integer

    total = 0
    For i = 0 To ArrayLen(values) - 1
        total = total + values[i]
    Next i
    Return total
End Function

Dim scores(5) As Integer
Dim result As Integer

scores[0] = 10
scores[1] = 20
result = Sum(scores)

The rank in the declaration must match the rank of the array passed at the call site. Passing a scalar or an array of the wrong rank is a compiler error.

You can also pass a single row of a multi-dimensional array to a one-dimensional array parameter by indexing the first dimension at the call site:

Dim grid(4, 8) As Integer
result = Sum(grid[2])

See Arrays for a full beginner-friendly walkthrough, including the sub-array passing pattern.

Return

Return
Return <expression>

Return
Return x + y