a little note to self and everybody.

zig has a weird but clever thing. for example, if you do a function signature like this:

```zig
fn func(param: Type) void {}
```

the compiler will decide by itself whether this `param` thingy should be copied or passed by reference. this kind of notation specifies "pass immutably", so the compiler takes control over copying/referencing. to specify that you want exactly a reference, you must define the function signature like the following:

```zig
fn func(param: *const Type) void {}
```

this will be useful.