Language tour

This tour is a quick, practical overview of mu’s core syntax and semantics.

Hello, mu 

fn main() {
  println("Hello World!")
}

main()

Variables and control flow 

x := 10
if x > 5 {
  println("x is big")
} else {
  println("x is small")
}

i := 0
while i < 3 {
  println(i)
  i = i + 1
}

Functions and closures 

fn make_counter() {
  n := 0
  return fn() {
    n = n + 1
    return n
  }
}

counter := make_counter()
println(counter())
println(counter())

Lists and maps 

nums := [1, 2, 3]
nums[1] = 42
println(nums)

user := {"name": "ada", "age": 42}
println(user.name)

Errors are values 

data := read("missing.txt")
if type(data) == "ERROR" {
  println("read failed:", data)
}

Truthiness

Falsey values include false, nil, 0, empty strings, empty lists/maps, and empty buffers.

status := if "" { "truthy" } else { "falsey" }
println(status)

Next steps