62 lines
818 B
V
62 lines
818 B
V
// Example of sum types
|
|
// Models a landing craft leaving orbit and landing on a world
|
|
import rand
|
|
import time
|
|
|
|
struct Moon {
|
|
}
|
|
|
|
struct Mars {
|
|
}
|
|
|
|
fn (m Mars) dust_storm() bool {
|
|
return rand.int() >= 0
|
|
}
|
|
|
|
struct Venus {
|
|
}
|
|
|
|
type World = Mars | Moon | Venus
|
|
|
|
struct Lander {
|
|
}
|
|
|
|
fn (l Lander) deorbit() {
|
|
println('leaving orbit')
|
|
}
|
|
fn (l Lander) open_parachutes(n int) {
|
|
println('opening $n parachutes')
|
|
}
|
|
|
|
fn wait() {
|
|
println('waiting...')
|
|
time.sleep(1 * time.second)
|
|
}
|
|
|
|
fn (l Lander) land(w World) {
|
|
if w is Mars {
|
|
for w.dust_storm() {
|
|
wait()
|
|
}
|
|
}
|
|
l.deorbit()
|
|
match w {
|
|
Moon {} // no atmosphere
|
|
Mars {
|
|
// light atmosphere
|
|
l.open_parachutes(3)
|
|
}
|
|
Venus {
|
|
// heavy atmosphere
|
|
l.open_parachutes(1)
|
|
}
|
|
}
|
|
println('landed')
|
|
}
|
|
|
|
fn main() {
|
|
l := Lander{}
|
|
l.land(Venus{})
|
|
l.land(Mars{})
|
|
}
|