weighted-gss 0.2.0

Persistent weighted graph-structured stacks
Documentation 
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/// A value associated with a structural stack path.
///
/// Weights use ordinary equality to identify values that can be factored over
/// one shared stack language. [`Weight::join`] must be associative, commutative,
/// and idempotent. These
/// laws make the extensional meaning independent of representation choices:
///
/// - `(a ⋁ b) ⋁ c = a ⋁ (b ⋁ c)`
/// - `a ⋁ b = b ⋁ a`
/// - `a ⋁ a = a`
pub trait Weight: Clone + PartialEq {
    /// Join two weights.
    fn join(&self, other: &Self) -> Self;
}

impl Weight for () {
    #[inline]
    fn join(&self, _other: &Self) -> Self {}
}