Hello World

Your first program

Create a file called hello.almd:

effect fn main() -> Result[Unit, String] = {
  println("Hello, world!")
  ok(())
}

Run it:

almide run hello.almd

Output:

Hello, world!

Breaking it down

• effect fn — this function has side effects (printing to stdout)
• main() — the entry point of the program
• -> Result[Unit, String] — returns Unit on success, or a String error
• println(...) — print a line to stdout
• ok(()) — return success with the Unit value ()

Adding logic

fn greet(name: String) -> String =
  "Hello, ${name}!"

effect fn main() -> Result[Unit, String] = {
  let names = ["Alice", "Bob", "Charlie"]
  for name in names {
    println(greet(name))
  }
  ok(())
}

Hello, Alice!
Hello, Bob!
Hello, Charlie!

Writing tests

Add a test block anywhere in your .almd file:

fn add(a: Int, b: Int) -> Int = a + b

test "addition" {
  assert_eq(add(1, 2), 3)
  assert_eq(add(0, 0), 0)
  assert_eq(add(-1, 1), 0)
}

Run tests:

almide test hello.almd

Building a binary

almide build hello.almd -o hello
./hello

Next steps

• Types & Values — learn about Almide’s type system
• Functions — pure functions and effect functions