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