src/hope_option.erl

   1 -module(hope_option).
   2
   3
   4 -export_type(
   5     [ t/1
   6     ]).
   7
   8 -export(
   9     [ put/2
  10     , get/2
  11     , map/2
  12     ]).
  13
  14
  15 -type t(A) ::
  16       none
  17     | {some, A}
  18     .
  19
  20
  21 put(X, F) ->
  22     case F(X)
  23     of  true  -> {some, X}
  24     ;   false -> none
  25     end.
  26
  27 get({some, X}, _) -> X;
  28 get(none     , Y) -> Y.
  29
  30 map({some, X}, F) -> {some, F(X)};
  31 map(none     , _) -> none.