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type | |
Either*[A, B] = object | |
case isA: bool | |
of true: | |
a: A | |
of false: | |
b: B | |
template isB(e: Either): bool = | |
not e.isA | |
func `$`*(e: Either): string = | |
if e.isA: | |
$e.a | |
else: | |
$e.b | |
func init*[A, B](_: typedesc[Either[A, B]]; a: sink A): Either[A, B] = | |
Either[A, B](isA: true, a: a) | |
func init*[A, B](_: typedesc[Either[A, B]]; b: sink B): Either[A, B] = | |
Either[A, B](isA: false, b: b) | |
func init*[A, B](_: typedesc[Either]; a: sink A; bType: typedesc[B]): Either[A, B] = | |
Either[A, B](isA: true, a: a) | |
func init*[A, B](_: typedesc[Either]; aType: typedesc[A]; b: sink B): Either[A, B] = | |
Either[A, B](isA: false, b: b) | |
func isOf*[A, B](e: Either[A, B]; _: typedesc[A]): bool = | |
e.isA | |
func isOf*[A, B](e: Either[A, B]; _: typedesc[B]): bool = | |
e.isB | |
func get*[A, B](e: Either[A, B]; _: typedesc[A]): lent A = | |
assert e.isA | |
e.a | |
func get*[A, B](e: Either[A, B]; _: typedesc[B]): lent B = | |
assert e.isB | |
e.b | |
func isLeft*[A, B](e: Either[A, B]): bool = | |
e.isA | |
func isRight*[A, B](e: Either[A, B]): bool = | |
e.isB | |
func left*[A, B](e: Either[A, B]): lent A = | |
assert e.isA | |
e.a | |
func right*[A, B](e: Either[A, B]): lent B = | |
assert e.isB | |
e.b | |
when isMainModule: | |
import std/sugar | |
block: | |
let e = Either.init(int, "hello") | |
dump typeof e | |
dump e | |
dump e.isOf(string) | |
dump e.isOf(int) | |
dump e.get(string) | |
dump e.isLeft | |
dump e.isRight | |
dump e.right | |
block: | |
let e = Either.init(42, int) | |
dump typeof e | |
dump e | |
dump compiles(e.isOf(int)) | |
dump compiles(e.get(int)) | |
dump e.isLeft | |
dump e.isRight | |
dump e.left |
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