qubit-function 0.16.0

Functional programming traits and Box/Rc/Arc adapters for Rust, inspired by Java functional interfaces
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// =============================================================================
//    Copyright (c) 2025 - 2026 Haixing Hu.
//
//    SPDX-License-Identifier: Apache-2.0
//
//    Licensed under the Apache License, Version 2.0.
// =============================================================================
//! Defines the `BoxConditionalBiConsumer` public type.

use {
    crate::BiConsumer,
    crate::BiPredicate,
    crate::BoxBiConsumer,
    crate::BoxBiPredicate,
    crate::consumers::macros::impl_box_conditional_consumer,
    crate::consumers::macros::impl_conditional_consumer_debug_display,
};

// =======================================================================
// 7. BoxConditionalBiConsumer - Box-based Conditional BiConsumer
// =======================================================================

/// BoxConditionalBiConsumer struct
///
/// A conditional non-mutating bi-consumer that only executes when a predicate
/// is satisfied. Uses `BoxBiConsumer` and `BoxBiPredicate` for single ownership
/// semantics.
///
/// This type is typically created by calling `BoxBiConsumer::when()` and is
/// designed to work with the `or_else()` method to create if-then-else logic.
///
/// # Features
///
/// - **Single Ownership**: Not cloneable, consumes `self` on use
/// - **Conditional Execution**: Only consumes when predicate returns `true`
/// - **Chainable**: Can add `or_else` branch to create if-then-else logic
/// - **Implements BiConsumer**: Can be used anywhere a `BiConsumer` is expected
/// - **Shared access**: Receives shared references; interior mutability and
///   external side effects remain possible
///
/// # Examples
///
/// ## Basic Conditional Execution
///
/// ```rust
/// use qubit_function::{BiConsumer, BoxBiConsumer};
///
/// let consumer = BoxBiConsumer::new(|x: &i32, y: &i32| {
///     println!("Both positive: {} + {} = {}", x, y, x + y);
/// });
/// let conditional = consumer.when(|x: &i32, y: &i32| *x > 0 && *y > 0);
///
/// conditional.accept(&5, &3);  // Prints: Both positive: 5 + 3 = 8
/// conditional.accept(&-5, &3); // Does nothing
/// ```
///
/// ## With or_else Branch
///
/// ```rust
/// use qubit_function::{BiConsumer, BoxBiConsumer};
///
/// let consumer = BoxBiConsumer::new(|x: &i32, y: &i32| {
///     println!("Both positive: {} + {} = {}", x, y, x + y);
/// })
/// .when(|x: &i32, y: &i32| *x > 0 && *y > 0)
/// .or_else(|x: &i32, y: &i32| {
///     println!("Not both positive: {} and {}", x, y);
/// });
///
/// consumer.accept(&5, &3);  // Prints: Both positive: 5 + 3 = 8
/// consumer.accept(&-5, &3); // Prints: Not both positive: -5 and 3
/// ```
#[must_use = "callback wrappers do nothing unless stored or invoked"]
pub struct BoxConditionalBiConsumer<T, U> {
    /// The wrapped consumer callback.
    pub(super) consumer: BoxBiConsumer<T, U>,
    /// The predicate controlling conditional execution.
    pub(super) predicate: BoxBiPredicate<T, U>,
}

// Use macro to generate conditional bi-consumer implementations
impl_box_conditional_consumer!(
    BoxConditionalBiConsumer<T, U>,
    BoxBiConsumer,
    BiConsumer
);

// Hand-written BiConsumer trait implementation
impl<T, U> BiConsumer<T, U> for BoxConditionalBiConsumer<T, U> {
    fn accept(&self, first: &T, second: &U) {
        if self.predicate.test(first, second) {
            self.consumer.accept(first, second);
        }
    }
}

// Use macro to generate Debug and Display implementations
impl_conditional_consumer_debug_display!(BoxConditionalBiConsumer<T, U>);