Variables

<type> <name> = <value>

All variables are constant and immutable by default

int a = 1
a = 2 // Error

To make a variable mutable, you can add the mut keyword

mut int b = 2
b = 3 // Works!

Shadowing

You can redefine variables with the same name within the same or lower scopes using shadowing, including changing the mutability of the variable.

test "shadowing" {
  int a = 10 // lets call this `a_1`

  // change mutability of a
  mut int a = 20 // different variable from `a_1`, let's call this `a_2`

  // change type of a
  str a = "hi" // different variable from `a_1` and `a_2`, let's call this `a_3`

  // redeclare within a lower scope
  {
    str a = "annyeonghaseyo" // different from `a_1`, `a_2`, and `a_3`, let's call this `a_4`
  }

  // `a_4` is no longer available, we're back to `a_3`
  assert a == "hi"
}

Discarding values

You can discard a value by assigning it to _:

fn hello() str {
  return "hello"
}

_ = hello() // discarded
_ = "hi" // discarded

Sigil ordering

Types are read from left to right. For instance, int[]? is a signed integer array that is optional, while int?[] is an array of signed integers that are optional.

int[]? arr = none
int?[] arr = [none]

int[]? arr = [none] // compile error: `int[]` cannot hold optional values
int?[] = none // compile error: attempted to assign `none` to a non-optional