1 | // Function signatures can be declared as types: |
2 | |
3 | type Filter = fn (string) string |
4 | |
5 | // Functions can accept function types as arguments: |
6 | |
7 | fn filter(s string, f Filter) string { |
8 | return f(s) |
9 | } |
10 | |
11 | // Declare a function with a matching signature: |
12 | |
13 | fn uppercase(s string) string { |
14 | return s.to_upper() |
15 | } |
16 | |
17 | fn main() { |
18 | // A function can be assigned to a matching type: |
19 | |
20 | my_filter := Filter(uppercase) |
21 | |
22 | // You don't strictly need the `Filter` cast - it's only used |
23 | // here to illustrate how these types are compatible. |
24 | |
25 | // All of the following prints "HELLO WORLD": |
26 | |
27 | println(filter('Hello world', my_filter)) |
28 | println(filter('Hello world', uppercase)) |
29 | println(filter('Hello world', fn (s string) string { |
30 | return s.to_upper() |
31 | })) |
32 | } |