Input and output

Printing

print(value) writes a value’s text to standard output; println(value) adds a newline. Both take a single argument — combine values with string interpolation:

let a = 6
let b = 7
println("{a} * {b} = {a * b}")   // 6 * 7 = 42

Any value prints, including records and arrays:

type Point = { x: int32, y: int32 }
println(Point { x: 1, y: 2 })

Reading input

input() reads one line from standard input, without the trailing newline. It returns string! (reading can fail), so unwrap it with ! — at the top level a failure just ends the program with the error — or handle it with match:

println("What's your name?")
let name = input()!
println("Hello, {name}!")

Files

read_file(path) and write_file(path, content) cover whole-file text I/O. Both return a Result. In a quick script, unwrap with ! and let a failure stop the program:

let path = "demo.txt"
write_file(path, "line one\nline two")!
let content = read_file(path)!
for line in content.split("\n") {
    println("  {line}")
}

Where a failure should be handled instead, match on the Result:

match read_file("missing.txt") {
    Ok { value } => println(value),
    Err { error } => println("read failed: {error}"),
}

For finer control, open(path, mode) returns a File!; a File has read(n), write(bytes), seek, size(), and close(), all returning Results, plus the File.stdin() / File.stdout() / File.stderr() constructors. See the standard library reference for the signatures.

Note: file I/O runs on the native runtime. The REPL interpreter (and the browser playground) refuses it at runtime — see the execution model reference.