Feature: support #local for constants and variables

[arjendevos]

#local works on function and types but not on constants or variables:

#local
const MY_CONSTANT = "value"  // error: the label can only be applied to type alias or fn

#local
var my_variable = "value"    // same error

Not sure whether or not this is done on purpose.

@weiwenhao are you open to proposals to improve this? I am not against #local but I think there are some other options worth considering.

[arjendevos]

@weiwenhao question about the globals, what is the purpose of them right now? Because you can't assign a value anymore to it? Is there going to be some init function where we can init the globals?

[weiwenhao]

@weiwenhao question about the globals, what is the purpose of them right now? Because you can't assign a value anymore to it? Is there going to be some init function where we can init the globals?

The primary purpose of global variables is data sharing across multiple coroutines (threads). In the future, I will support string v = ‘hello’ and [int] list = [1, 2, 3] similar to literal initialization. For declaring constants, const can be used as a substitute in most scenarios.

It is recommended to use fn init() to initialize complex global variables. However, unlike Go, the init function is not automatically called. You must manually call the init function after importing to complete initialization.

[weiwenhao]

As declared in the reserved keyword https://nature-lang.org/docs/syntax, I think hiding the api by default and exporting it via a pub declaration is a good way to go, especially when writing business which may be necessary.

pub type x
pub const
pub var
pub fn

[arjendevos]

I agree, I think it creates elegant syntax:

// Everything is private by default

// Constants
const INTERNAL_KEY = 'secret'           // private
pub const API_VERSION = '1.0.0'         // public

// Variables
var db_pool = 10                        // private
pub var max_retries = 3                 // public

// Functions
fn hash_password(string pw):string {    // private
    return '...'
}

pub fn login(string email, string pw):bool {  // public
    var hashed = hash_password(pw)
    return true
}

// Types
type db_config = struct {               // private
    string host
    int port
}

pub type user_t = struct {              // public
    string name
    string email
}

I do have a question regarding the = when declaring types, is there a specific reason for that? Because It does make it feel a bit off imo, just curious.

[weiwenhao]

The equal sign is more distinguishable as a separator

type temp_t<T, U>: addable struct {

}

type temp_t<T, U>: addable = struct{

}