var f0 = new Fn { IO.print("zero") }
var f1 = new Fn {|a| IO.print("one " + a) }
var f2 = new Fn {|a, b| IO.print("two " + a + " " + b) }
var f3 = new Fn {|a, b, c| IO.print("three " + a + " " + b + " " + c) }

f0.call("a") // expect: zero
f0.call("a", "b") // expect: zero

f1.call("a", "b") // expect: one a
f1.call("a", "b", "c") // expect: one a

f2.call("a", "b", "c") // expect: two a b
f2.call("a", "b", "c", "d") // expect: two a b

f3.call("a", "b", "c", "d") // expect: three a b c
f3.call("a", "b", "c", "d", "e") // expect: three a b c