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. |