//@NO-IMPLICIT-PRELUDE
//! Implementation of the `Alternative` type
let { Applicative } = import! std.applicative

/// A monoid on applicative functors.
#[implicit]
type Alternative f = {
    applicative : Applicative f,
    /// The identify of `or`
    empty : forall a . f a,
    /// An associative binary operation.
    ///
    /// Evaluates to the first argument if it is not `empty`, otherwise evaluates to the second argument.
    or : forall a . f a -> f a -> f a
}

let empty ?alt : [Alternative f] -> f a = alt.empty

let or ?alt : [Alternative f] -> f a -> f a -> f a = alt.or

/// An associative binary operation. Alias of `or`.
///
/// Evaluates to the first argument if it is not `empty`, otherwise evaluates to the second argument.
#[infix(left, 3)]
let (<|>) : [Alternative f] -> f a -> f a -> f a = or

{
    Alternative,
    empty,
    or,
    (<|>),
}