-module(hope_option).
--behavior(hope_monad).
+-behavior(hope_gen_monad).
-export_type(
[ t/1
]).
-export(
- [ put/2
- , get/2
- , return/1
+ % Generic monad interface
+ [ return/1
, map/2
- , iter/2
, pipe/2
+
+ % Specific to hope_option:t()
+ , return/2
+ , put/2
+ , get/2
+ , iter/2
, of_result/1
, of_undefined/1
]).
-spec put(A, fun((A) -> boolean())) ->
t(A).
put(X, F) ->
- case F(X)
- of true -> {some, X}
- ; false -> none
- end.
+ return(X, F).
-spec get(t(A), Default :: A) ->
A.
return(X) ->
{some, X}.
+-spec return(A, fun((A) -> boolean())) ->
+ t(A).
+return(X, Condition) ->
+ case Condition(X)
+ of true -> {some, X}
+ ; false -> none
+ end.
+
-spec map(t(A), fun((A) -> (B))) ->
t(B).
map({some, X}, F) -> {some, F(X)};