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//! Reference-counted pointers with shared ownership, unwrapping, and take-cell capabilities.
//!
//! In addition to cloneable shared pointers, this module provides a
//! [`TakeCellOf`](RefCountedPointer::TakeCellOf) abstraction: a cloneable cell
//! that holds a value which can be taken exactly once. This pairs the
//! appropriate interior mutability primitive with each pointer type
//! (`RefCell` for `Rc`, `Mutex` for `Arc`), enabling move-out-of-closure
//! patterns while preserving thread safety when needed.
//!
//! ### Examples
//!
//! ```
//! use fp_library::{
//! brands::*,
//! functions::*,
//! };
//!
//! let ptr = ref_counted_pointer_new::<RcBrand, _>(42);
//! let clone = ptr.clone();
//! assert_eq!(*clone, 42);
//!
//! let cell = take_cell_new::<RcBrand, _>(99);
//! let cell_clone = cell.clone();
//! assert_eq!(take_cell_take::<RcBrand, _>(&cell), Some(99));
//! assert_eq!(take_cell_take::<RcBrand, _>(&cell_clone), None);
//! ```
#[fp_macros::document_module]
mod inner {
use {
fp_macros::*,
std::ops::Deref,
};
/// Trait for reference-counted pointers with shared ownership.
///
/// Provides [`Of`](Self::Of) (a cloneable, dereferenceable pointer)
/// and [`TakeCellOf`](Self::TakeCellOf) (a cloneable cell supporting one-shot value
/// extraction). The latter pairs the pointer with an appropriate interior mutability
/// primitive (`RefCell` for `Rc`, `Mutex` for `Arc`).
///
/// This is an independent trait (not a supertrait of
/// [`Pointer`](crate::classes::Pointer)). Both `RcBrand` and `ArcBrand`
/// implement `Pointer` and `RefCountedPointer` independently.
pub trait RefCountedPointer {
/// The cloneable pointer type constructor.
///
/// For Rc/Arc, this is the same as `Of<'a, T>`.
type Of<'a, T: ?Sized + 'a>: Clone + Deref<Target = T> + 'a;
/// Wraps a sized value in a cloneable pointer.
#[document_signature]
///
#[document_type_parameters("The lifetime of the value.", "The type of the value to wrap.")]
///
#[document_parameters("The value to wrap.")]
///
#[document_returns("The value wrapped in the cloneable pointer type.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let ptr = ref_counted_pointer_new::<RcBrand, _>(42);
/// assert_eq!(*ptr, 42);
/// ```
fn new<'a, T: 'a>(value: T) -> Self::Of<'a, T>
where
Self::Of<'a, T>: Sized;
/// Attempts to unwrap the inner value if this is the sole reference.
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the wrapped value.",
"The type of the wrapped value."
)]
///
#[document_parameters("The pointer to attempt to unwrap.")]
///
#[document_returns("`Ok(value)` if this is the sole reference, otherwise `Err(ptr)`.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let ptr = ref_counted_pointer_new::<RcBrand, _>(42);
/// assert_eq!(try_unwrap::<RcBrand, _>(ptr), Ok(42));
///
/// let ptr1 = ref_counted_pointer_new::<RcBrand, _>(42);
/// let ptr2 = ptr1.clone();
/// assert!(try_unwrap::<RcBrand, _>(ptr1).is_err());
/// ```
fn try_unwrap<'a, T: 'a>(ptr: Self::Of<'a, T>) -> Result<T, Self::Of<'a, T>>;
/// A cloneable cell that holds an optional value which can be taken exactly once.
///
/// For [`RcBrand`](crate::brands::RcBrand), this is `Rc<RefCell<Option<T>>>`.
/// For [`ArcBrand`](crate::brands::ArcBrand), this is `Arc<Mutex<Option<T>>>`.
type TakeCellOf<'a, T: 'a>: Clone + 'a;
/// Creates a new take-cell containing the given value.
#[document_signature]
///
#[document_type_parameters("The lifetime of the value.", "The type of the value to store.")]
///
#[document_parameters("The value to store in the cell.")]
///
#[document_returns("A new take-cell containing the value.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let cell = take_cell_new::<RcBrand, _>(42);
/// assert_eq!(take_cell_take::<RcBrand, _>(&cell), Some(42));
/// ```
fn take_cell_new<'a, T: 'a>(value: T) -> Self::TakeCellOf<'a, T>;
/// Takes the value out of the cell, leaving `None` behind.
///
/// Returns `Some(value)` the first time, `None` on subsequent calls.
#[document_signature]
///
#[document_type_parameters("The lifetime of the value.", "The type of the stored value.")]
///
#[document_parameters("The cell to take the value from.")]
///
#[document_returns("`Some(value)` if the cell still contains a value, `None` otherwise.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let cell = take_cell_new::<RcBrand, _>(42);
/// assert_eq!(take_cell_take::<RcBrand, _>(&cell), Some(42));
/// assert_eq!(take_cell_take::<RcBrand, _>(&cell), None);
/// ```
fn take_cell_take<'a, T: 'a>(cell: &Self::TakeCellOf<'a, T>) -> Option<T>;
}
/// Attempts to unwrap the inner value if this is the sole reference.
///
/// Free function version that dispatches to [the type class' associated function][`RefCountedPointer::try_unwrap`].
#[document_signature]
///
#[document_type_parameters(
"The pointer brand.",
"The lifetime of the wrapped value.",
"The type of the wrapped value."
)]
///
#[document_parameters("The pointer to attempt to unwrap.")]
///
#[document_returns("`Ok(value)` if this is the sole reference, otherwise `Err(ptr)`.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let ptr = ref_counted_pointer_new::<RcBrand, _>(42);
/// assert_eq!(try_unwrap::<RcBrand, _>(ptr), Ok(42));
///
/// let ptr1 = ref_counted_pointer_new::<RcBrand, _>(42);
/// let ptr2 = ptr1.clone();
/// assert!(try_unwrap::<RcBrand, _>(ptr1).is_err());
/// ```
pub fn try_unwrap<'a, P: RefCountedPointer, T: 'a>(
ptr: P::Of<'a, T>
) -> Result<T, P::Of<'a, T>> {
P::try_unwrap(ptr)
}
/// Wraps a sized value in a cloneable pointer.
#[document_signature]
///
#[document_type_parameters(
"The pointer brand.",
"The lifetime of the value.",
"The type of the value to wrap."
)]
///
#[document_parameters("The value to wrap.")]
///
#[document_returns("The value wrapped in the cloneable pointer type.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// classes::*,
/// functions::*,
/// };
///
/// let ptr = ref_counted_pointer_new::<RcBrand, _>(42);
/// let clone = ptr.clone();
/// assert_eq!(*clone, 42);
/// ```
pub fn new<'a, P: RefCountedPointer, T: 'a>(value: T) -> P::Of<'a, T>
where
P::Of<'a, T>: Sized, {
P::new(value)
}
/// Creates a new take-cell containing the given value.
///
/// Free function version that dispatches to [the type class' associated function][`RefCountedPointer::take_cell_new`].
#[document_signature]
///
#[document_type_parameters(
"The pointer brand.",
"The lifetime of the value.",
"The type of the value to store."
)]
///
#[document_parameters("The value to store in the cell.")]
///
#[document_returns("A new take-cell containing the value.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let cell = take_cell_new::<RcBrand, _>(42);
/// assert_eq!(take_cell_take::<RcBrand, _>(&cell), Some(42));
/// ```
pub fn take_cell_new<'a, P: RefCountedPointer, T: 'a>(value: T) -> P::TakeCellOf<'a, T> {
P::take_cell_new(value)
}
/// Takes the value out of a take-cell, leaving `None` behind.
///
/// Free function version that dispatches to [the type class' associated function][`RefCountedPointer::take_cell_take`].
#[document_signature]
///
#[document_type_parameters(
"The pointer brand.",
"The lifetime of the value.",
"The type of the stored value."
)]
///
#[document_parameters("The cell to take the value from.")]
///
#[document_returns("`Some(value)` if the cell still contains a value, `None` otherwise.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let cell = take_cell_new::<RcBrand, _>(42);
/// assert_eq!(take_cell_take::<RcBrand, _>(&cell), Some(42));
/// assert_eq!(take_cell_take::<RcBrand, _>(&cell), None);
/// ```
pub fn take_cell_take<'a, P: RefCountedPointer, T: 'a>(
cell: &P::TakeCellOf<'a, T>
) -> Option<T> {
P::take_cell_take(cell)
}
}
pub use inner::*;