Support for constants?

[Alex Spurling]

Is it possible to declare constant values in Onyx? If not, it would be useful to add support for them. Here is an example of what I mean:

use core {println}

CHECKERBOARD_SIZE: i32 = 20;
CHECKERBOARD_BUFFER_SIZE: i32 = CHECKERBOARD_SIZE * CHECKERBOARD_SIZE * 4;

main :: () {
    generateCheckerBoard();
}

generateCheckerBoard :: () {
    for x: 0 .. CHECKERBOARD_SIZE {
        for y: 0 .. CHECKERBOARD_SIZE {
            println(x);
        }
    }
}

Here the value of the two constants CHECKERBOARD_SIZE and CHECKERBOARD_BUFFER_SIZE should be calculated at compile time. Currently using this syntax in Onyx 0.1.8 results in the error "Top level expressions must be compile time known."

[Brendan Hansen]

Onyx does have support for constants. The way you would do it to use a :: instead of :=. So your top two lines would be:

CHECKERBOARD_SIZE :: 10
CHECKERBOARD_BUFFER_SIZE :: CHECKERBOARD_SIZE * CHECKERBOARD_SIZE

This will will make them constant and compile time know. Hope this helps!

[Alex Spurling]

Great thanks. I might raise another issue to add a mention of this syntax to the docs.

[Brendan Hansen]

I do need to clarify it in the docs for sure. It is mentioned in the Bindings section, but I don't explicitly say that you can use it with numeric values like that. I will leave this issue open until those docs are updated.

[Alex Spurling]

Is it possible to define fixed arrays as constants? When I try to compile this I get the error "Binary operator '[]' not understood for arguments of type 'type_expr' and 'unsized int'."

use core {println}

CHECKERBOARD_SIZE :: 20;
CHECKERBOARD_BUFFER_SIZE :: CHECKERBOARD_SIZE * CHECKERBOARD_SIZE * 4;
CHECKERBOARD_BUFFER_POINTER :: [CHECKERBOARD_BUFFER_SIZE] i32;

main :: () {
    CHECKERBOARD_BUFFER_POINTER[3] = 2;
}

I want to define an area of memory that can be exported from the wasm module and referenced by the javascript runtime. I am trying to translate this AssemblyScript example to Onyx: https://wasmbyexample.dev/examples/reading-and-writing-graphics/reading-and-writing-graphics.assemblyscript.en-us.html

[Brendan Hansen]

So let me explain this a little bit. The line,

CHECKERBOARD_BUFFER_POINTER :: [CHECKERBOARD_BUFFER_SIZE] i32;

is actually binding CHECKERBOARD_BUFFER_POINTER as a type alias to the type [1600] i32, or a fixed-sized array of i32 that is 1600 elements long.

What you actually want is simply to remove one colon:

CHECKERBOARD_BUFFER_POINTER: [CHECKERBOARD_BUFFER_SIZE] i32;

This makes CHECKERBOARD_BUFFER_POINTER a global variable of type [1600] i32.

Hope this makes sense!

[Brendan Hansen]

The documentation has been updated and is now live, so I am going to close this issue.