[hope.git] / src / hope_option.erl

-module(hope_option).


-export_type(
    [ t/1
    ]).

-export(
    [ put/2
    , get/2
    , map/2
    ]).


-type t(A) ::
      none
    | {some, A}
    .


-spec put(A, fun((A) -> boolean())) ->
    t(A).
put(X, F) ->
    case F(X)
    of  true  -> {some, X}
    ;   false -> none
    end.

-spec get(t(A), Default :: A) ->
    A.
get({some, X}, _) -> X;
get(none     , Y) -> Y.

-spec map(t(A), fun((A) -> (B))) ->
    t(B).
map({some, X}, F) -> {some, F(X)};
map(none     , _) -> none.
Commit	Line	Data
	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	-spec put(A, fun((A) -> boolean())) ->
	22	t(A).
	23	put(X, F) ->
	24	case F(X)
	25	of true -> {some, X}
	26	; false -> none
	27	end.
	28
	29	-spec get(t(A), Default :: A) ->
	30	A.
	31	get({some, X}, _) -> X;
	32	get(none , Y) -> Y.
	33
	34	-spec map(t(A), fun((A) -> (B))) ->
	35	t(B).
	36	map({some, X}, F) -> {some, F(X)};
	37	map(none , _) -> none.