2. Values, types and functions

let binds immutably, var mutably. The primitive types are Int, Float, Bool and String. A top-level function has to write out every parameter type and its return type — the signature is the contract.

fn square(x: Int) -> Int = x * x

fn abs(x: Int) -> Int =
  if x < 0 { 0 - x } else { x }

pub fn main() -> Unit !io = {
  var total = 0
  total = total + square(3)
  total = total + abs(-4)
  println(to_string(total))
}

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The pipe |> puts its left-hand side into the first argument of the call on its right, so a line reads in the direction the data flows:

fn double(x: Int) -> Int = x * 2
fn inc(x: Int) -> Int = x + 1

pub fn main() -> Unit !io =
  5 |> double |> inc |> to_string |> println

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