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retired
A standard library for the Gleam programming language
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src/gleam/order.gleam
/// Represents the result of a single comparison to determine the precise
/// ordering of two values.
///
pub type Order {
/// Less-than
Lt
/// Equal
Eq
/// Greater than
Gt
}
/// Inverts an order, so less-than becomes greater-than and greater-than
/// becomes less-than.
///
/// ## Examples
///
/// ```gleam
/// negate(Lt)
/// // -> Gt
/// ```
///
/// ```gleam
/// negate(Eq)
/// // -> Eq
/// ```
///
/// ```gleam
/// negate(Lt)
/// // -> Gt
/// ```
///
pub fn negate(order: Order) -> Order {
case order {
Lt -> Gt
Eq -> Eq
Gt -> Lt
}
}
/// Produces a numeric representation of the order.
///
/// ## Examples
///
/// ```gleam
/// to_int(Lt)
/// // -> -1
/// ```
///
/// ```gleam
/// to_int(Eq)
/// // -> 0
/// ```
///
/// ```gleam
/// to_int(Gt)
/// // -> 1
/// ```
///
pub fn to_int(order: Order) -> Int {
case order {
Lt -> -1
Eq -> 0
Gt -> 1
}
}
/// Compares two `Order` values to one another, producing a new `Order`.
///
/// ## Examples
///
/// ```gleam
/// compare(Eq, with: Lt)
/// // -> Gt
/// ```
///
pub fn compare(a: Order, with b: Order) -> Order {
case a, b {
x, y if x == y -> Eq
Lt, _ | Eq, Gt -> Lt
_, _ -> Gt
}
}
/// Returns the largest of two orders given that `Gt > Eq > Lt`.
///
/// ## Examples
///
/// ```gleam
/// max(Eq, Lt)
/// // -> Eq
/// ```
///
pub fn max(a: Order, b: Order) -> Order {
case a, b {
Gt, _ -> Gt
Eq, Lt -> Eq
_, _ -> b
}
}
/// Returns the smallest of two orders given that `Gt > Eq > Lt`.
///
/// ## Examples
///
/// ```gleam
/// min(Eq, Lt)
/// // -> Lt
/// ```
///
pub fn min(a: Order, b: Order) -> Order {
case a, b {
Lt, _ -> Lt
Eq, Gt -> Eq
_, _ -> b
}
}
/// Inverts an ordering function, so less-than becomes greater-than and greater-than
/// becomes less-than.
///
/// ## Examples
///
/// ```gleam
/// import gleam/int
/// import gleam/list
/// list.sort([1, 5, 4], by: reverse(int.compare))
/// // -> [5, 4, 1]
/// ```
///
pub fn reverse(orderer: fn(a, a) -> Order) -> fn(a, a) -> Order {
fn(a, b) { orderer(b, a) }
}