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//! Cloneable wrappers over closures for generic handling of functions in higher-kinded contexts.
//!
//! The [`CloneFn`] trait defines the type of the wrapper, parameterized by
//! a [`ClosureMode`](crate::dispatch::ClosureMode) that determines whether the
//! wrapped closure takes owned values ([`Val`](crate::dispatch::Val)) or
//! references ([`Ref`](crate::dispatch::Ref)).
//!
//! The [`LiftFn`] trait provides construction of Val-mode wrapped functions.
//!
//! ### Examples
//!
//! ```
//! use fp_library::{
//! brands::*,
//! functions::*,
//! };
//!
//! let f = lift_fn_new::<RcFnBrand, _, _>(|x: i32| x * 2);
//! assert_eq!(f(5), 10);
//! ```
#[fp_macros::document_module]
mod inner {
use {
crate::{
classes::RefCountedPointer,
dispatch::{
ClosureMode,
Ref,
Val,
},
},
fp_macros::*,
std::ops::Deref,
};
/// A trait for cloneable wrappers over closures, parameterized by closure mode.
///
/// This trait is implemented by "Brand" types (like [`RcFnBrand`][crate::brands::RcFnBrand])
/// to provide a way to type-check cloneable wrappers over closures (`Rc<dyn Fn...>` or
/// `Arc<dyn Fn...>`) in a generic context.
///
/// The `Mode` parameter determines the `Deref` target:
/// - [`Val`]: wraps `Fn(A) -> B` (by-value closures)
/// - [`Ref`]: wraps `Fn(&A) -> B` (by-reference closures)
///
/// The default mode is [`Val`], so existing code using `CloneFn` without
/// a mode parameter is unchanged.
///
/// For construction of wrapped functions, see [`LiftFn`].
#[document_type_parameters(
"The closure mode. Either [`Val`] (by-value, default) or [`Ref`] (by-reference)."
)]
pub trait CloneFn<Mode: ClosureMode = Val> {
/// The pointer brand backing this function wrapper.
///
/// Each `CloneFn` implementor is backed by exactly one reference-counted
/// pointer type. For [`FnBrand<P>`](crate::brands::FnBrand), this is `P`.
type PointerBrand: RefCountedPointer;
/// The type of the cloneable function wrapper.
///
/// This associated type represents the concrete type of the wrapper (e.g., `Rc<dyn Fn(A) -> B>`)
/// that implements `Clone` and dereferences to the underlying closure.
type Of<'a, A: 'a, B: 'a>: 'a + Clone + Deref<Target = Mode::Target<'a, A, B>>;
}
/// A trait for constructing Val-mode cloneable function wrappers from closures.
///
/// This is separated from [`CloneFn`] because the closure parameter type
/// (`Fn(A) -> B`) is specific to [`Val`] mode. For by-reference mode
/// construction, see [`RefLiftFn`].
pub trait LiftFn: CloneFn<Val> {
/// Creates a new cloneable function wrapper.
///
/// This function wraps the provided closure `f` into a cloneable function.
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the function and its captured data.",
"The input type of the function.",
"The output type of the function."
)]
///
#[document_parameters("The closure to wrap.")]
#[document_returns("The wrapped cloneable function.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let f = lift_fn_new::<RcFnBrand, _, _>(|x: i32| x * 2);
/// assert_eq!(f(5), 10);
/// ```
fn new<'a, A: 'a, B: 'a>(f: impl 'a + Fn(A) -> B) -> <Self as CloneFn>::Of<'a, A, B>;
}
/// Creates a new cloneable function wrapper.
///
/// Free function version that dispatches to [the type class' associated function][`LiftFn::new`].
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the function and its captured data.",
"The brand of the cloneable function wrapper.",
"The input type of the function.",
"The output type of the function."
)]
///
#[document_parameters("The closure to wrap.")]
#[document_returns("The wrapped cloneable function.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let f = lift_fn_new::<RcFnBrand, _, _>(|x: i32| x * 2);
/// assert_eq!(f(5), 10);
/// ```
pub fn new<'a, Brand, A, B>(f: impl 'a + Fn(A) -> B) -> <Brand as CloneFn>::Of<'a, A, B>
where
Brand: LiftFn, {
<Brand as LiftFn>::new(f)
}
/// A trait for constructing Ref-mode cloneable function wrappers from closures.
///
/// This mirrors [`LiftFn`] but for by-reference closures (`Fn(&A) -> B`).
pub trait RefLiftFn: CloneFn<Ref> {
/// Creates a new cloneable by-reference function wrapper.
///
/// This function wraps the provided closure `f` (which takes `&A`)
/// into a cloneable function.
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the function and its captured data.",
"The input type (the closure receives `&A`).",
"The output type of the function."
)]
///
#[document_parameters("The by-reference closure to wrap.")]
#[document_returns("The wrapped cloneable by-reference function.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let f = ref_lift_fn_new::<RcFnBrand, _, _>(|x: &i32| *x * 2);
/// assert_eq!(f(&5), 10);
/// ```
fn ref_new<'a, A: 'a, B: 'a>(
f: impl 'a + Fn(&A) -> B
) -> <Self as CloneFn<Ref>>::Of<'a, A, B>;
}
/// Creates a new cloneable by-reference function wrapper.
///
/// Free function version that dispatches to [`RefLiftFn::ref_new`].
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the function and its captured data.",
"The brand of the cloneable function wrapper.",
"The input type (the closure receives `&A`).",
"The output type of the function."
)]
///
#[document_parameters("The by-reference closure to wrap.")]
#[document_returns("The wrapped cloneable by-reference function.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let f = ref_lift_fn_new::<RcFnBrand, _, _>(|x: &i32| *x * 2);
/// assert_eq!(f(&5), 10);
/// ```
pub fn ref_new<'a, Brand, A, B>(
f: impl 'a + Fn(&A) -> B
) -> <Brand as CloneFn<Ref>>::Of<'a, A, B>
where
Brand: RefLiftFn, {
<Brand as RefLiftFn>::ref_new(f)
}
}
pub use inner::*;