gear-common 2.0.0

// Copyright (C) Gear Technologies Inc.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

//! Module for counting primitive.
//!
//! Counting primitives are able to return the information
//! about amount of elements they contain.

/// Represents default counting logic, by providing ability
/// to return length of the object as specified (associated) type
/// or answer the question is the object empty.
pub trait Counted {
    /// Returning length type.
    type Length: Default + PartialEq;

    /// Returns current Self's amount of elements as `Length` type.
    fn len() -> Self::Length;

    /// Returns bool, defining if Self doesn't contain elements.
    fn is_empty() -> bool {
        Self::len() == Default::default()
    }
}

/// Represents default counting logic, by providing ability
/// to return length of the object as specified (associated) type
/// or answer the question is the object empty, by provided key of
/// specified (associated) type.
///
/// Should be implemented on double map based types.
pub trait CountedByKey {
    /// Key type of counting target.
    type Key;
    /// Returning length type.
    type Length: Default + PartialEq;

    /// Returns current Self's amount of elements as `Length` type.
    fn len(key: &Self::Key) -> Self::Length;

    /// Returns bool, defining if Self doesn't contain elements.
    fn is_empty(key: &Self::Key) -> bool {
        Self::len(key) == Default::default()
    }
}