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