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use std::convert::From;
#[derive(Clone, Copy, Eq, PartialEq, Ord, PartialOrd)]
pub enum TriState {
Yes,
No,
Unknown
}
impl TriState {
pub fn yes(self) -> bool { self == TriState::Yes }
pub fn no(self) -> bool { self == TriState::No }
pub fn unknown(self) -> bool { self == TriState::Unknown }
pub fn definitely(self) -> bool { self.yes() }
pub fn definitely_not(self) -> bool { self.no() }
pub fn to_bool(self) -> Option<bool> {
match self {
TriState::Yes => Some(true),
TriState::No => Some(false),
TriState::Unknown => None
}
}
}
impl From<TriState> for Option<bool> {
fn from(t: TriState) -> Option<bool> { t.to_bool() }
}
impl From<Option<bool>> for TriState {
fn from(b: Option<bool>) -> TriState {
match b {
Some(true) => TriState::Yes,
Some(false) => TriState::No,
None => TriState::Unknown
}
}
}
impl From<bool> for TriState {
fn from(b: bool) -> TriState {
match b {
true => TriState::Yes,
false => TriState::No
}
}
}