type foobar is map(int, int)

const fb : foobar = map
  23 -> 0 ;
  42 -> 0 ;
end

function set_ (var n : int ; var m : foobar) : foobar is block {
  m[23] := n ;
} with m


function rm (var m : foobar) : foobar is block {
  remove 42 from map m
} with m

function size_ (const m : foobar) : nat is
  block {skip} with (size(m))

function gf (const m : foobar) : int is begin skip end with get_force(23, m)

function get (const m : foobar) : option(int) is
  begin
    skip
  end with m[42]

const bm : foobar = map
  144 -> 23 ;
  51 -> 23 ;
  42 -> 23 ;
  120 -> 23 ;
  421 -> 23 ;
end