Type checking

nbs = [ 1, 2, 5, 3 ]
i = maximum(nbs)  #=> 5

nbs = [ 1, 2, 5, "foo" ]
i = maximum(nbs)   #=> ill-typed at compile-time


name, size = s.m("(\w+):(\d+)")
  # example of valid s = "foo:100"

"%d has %0.2f\n".printf(name.capitalize)
  #=> error missing argument to printf

"%d has %0.2f\n".printf(name.capitalize, size / 10)
  #=> error name.capitalize is not a number

"%s has %0.2f\n".printf(name.capitalize, size / 10)