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$ifndef _OPTION
$define _OPTION
// The option type is treated specially by the lem backend, so it maps
// onto the lem maybe type. If the constructors are named differently,
// this won't work - also no other type should be created with
// constructors named Some or None.
union option('a: Type) = {
Some : 'a,
None : unit
}
val is_none : forall ('a : Type). option('a) -> bool
function is_none opt = match opt {
Some(_) => false,
None() => true
}
val is_some : forall ('a : Type). option('a) -> bool
function is_some opt = match opt {
Some(_) => true,
None() => false
}
$endif
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