RosettaCodeData/Task/Ackermann-function/Wren/ackermann-function.wren

// To use recursion definition and declaration must be on separate lines
var Ackermann
Ackermann = Fn.new {|m, n|
    if (m == 0) return n + 1
    if (n == 0) return Ackermann.call(m - 1, 1)
    return Ackermann.call(m - 1, Ackermann.call(m, n - 1))
}