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     , iter/2
  13     , of_result/1
  14     ]).
  15
  16
  17 -type t(A) ::
  18       none
  19     | {some, A}
  20     .
  21
  22
  23 -spec put(A, fun((A) -> boolean())) ->
  24     t(A).
  25 put(X, F) ->
  26     case F(X)
  27     of  true  -> {some, X}
  28     ;   false -> none
  29     end.
  30
  31 -spec get(t(A), Default :: A) ->
  32     A.
  33 get({some, X}, _) -> X;
  34 get(none     , Y) -> Y.
  35
  36 -spec map(t(A), fun((A) -> (B))) ->
  37     t(B).
  38 map({some, X}, F) -> {some, F(X)};
  39 map(none     , _) -> none.
  40
  41 -spec iter(t(A), fun((A) -> (ok))) ->
  42     ok.
  43 iter({some, X}, F) -> ok = F(X);
  44 iter(none     , _) -> ok.
  45
  46 -spec of_result(hope_result:t(A, _B)) ->
  47     t(A).
  48 of_result({ok, X})    -> {some, X};
  49 of_result({error, _}) -> none.