Modules

Import statements import the whole module and assign it to a variable. Specific things from the module cannot be imported, such as JavaScript's import { function } from pkg or Python's from pkg import function. Wildcard imports like Python's from pkg import * are also not allowed.

import "std/math" as math

rat phi = (math.sqrt(5.0) + 1.0) / 2.0

This is beneficial because different modules can export functions with the same name, and it'll always be clear where each function came from, at the cost of typing slightly more.

Each file is a module, and you can import from files by using the import keyword, and assign it to a variable with as.

import "path/to/mod" as someMod

This variable is a special struct containing all of the exported symbols from a module, along with their (non-exported) dependencies. This is useful, for instance, if an exported function has side effects. For example:

// std/math

pub rat PI = 3.14159265358979323

pub uint MIN_UINT = 0
pub uint MAX_UINT = 0xffffffffffffffff

pub int MIN_INT = -0x7fffffffffffffff
pub int MAX_INT = 0x7fffffffffffffff

// random number generator
// this is an example of something that might depend on non-exported symbols
int A = 8121
int C = 28411
int M = 134456
mut int seed = 123456789
pub fn randomLCG() -> int {
  seed = (A * seed + C) % M
  return seed
}

would get turned into:

module {
  pub rat PI = 3.14159265358979323

  pub uint MIN_UINT = 0
  pub uint MAX_UINT = 0xffffffffffffffff

  pub int MIN_INT = -0x7fffffffffffffff
  pub int MAX_INT = 0x7fffffffffffffff

  mut int seed = 123456789
  pub fn randomLCG() -> int {
    seed = (8121 * seed + 28411) % 134456
    return seed
  }
}

You would then be able to use this as:

import "std/math" as math

println("pi = {math.PI}") // pi = 3.14159265358979323
println("{math.MIN_UINT} <= uint <= {math.MAX_UINT}") // 0 <= uint <= ...
println(randomLCG()) // 69376

Exporting symbols

As noted in the example above, symbols can be exported using the pub keyword. This includes variables, functions, etc.

There are some additional rules for exporting fields and methods in structs, which you can read about in the structs documentation.