Take Milo for a walk

Learn the language by running it — edit each program, run it in your browser, move to the next. Real compiler, real output, no install.

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Learn the basics in 11 steps

Edit each program, run it, move to the next. Real compiler, real output — no install.

Step 1 of 11

1. Values that can’t surprise you

A let binding is immutable; a var is mutable. You opt in to change.

values.milo

fn main(): i32 {
    let name = "Milo"        // immutable
    var count = 0            // mutable
    count = count + 3
    print($"hello from {name}, count = {count}")
    return 0
}

fn main(): i32 { let name = "Milo" // immutable var count = 0 // mutable count = count + 3 print($"hello from {name}, count = {count}") return 0 }

outputloading compiler…

// edit the code, then press Run

takeawayImmutable by default — you always know what can change out from under you.

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