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//! Owned heap-allocated pointer abstraction using [`Box`].
//!
//! Provides trait implementations for using `Box` in the library's pointer abstraction.
//! `BoxBrand` implements [`Pointer`](crate::classes::Pointer) and
//! [`ToDynFn`](crate::classes::ToDynFn) but not
//! [`RefCountedPointer`](crate::classes::RefCountedPointer)
//! (since `Box<dyn Fn>` is not `Clone`).
//!
//! ### Examples
//!
//! ```
//! use fp_library::{
//! brands::*,
//! classes::*,
//! };
//!
//! let ptr = <BoxBrand as Pointer>::new(42);
//! assert_eq!(*ptr, 42);
//! ```
#[fp_macros::document_module]
mod inner {
use {
crate::{
brands::BoxBrand,
classes::{
Pointer,
ToDynFn,
},
},
fp_macros::*,
};
impl Pointer for BoxBrand {
type Of<'a, T: ?Sized + 'a> = Box<T>;
/// Wraps a sized value in a `Box`.
#[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 a `Box`.")]
///
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// classes::*,
/// };
///
/// let ptr = <BoxBrand as Pointer>::new(42);
/// assert_eq!(*ptr, 42);
/// ```
fn new<'a, T: 'a>(value: T) -> Box<T> {
Box::new(value)
}
}
impl ToDynFn for BoxBrand {
/// Coerces a sized closure to a `dyn Fn` wrapped in a `Box`.
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the closure.",
"The input type of the function.",
"The output type of the function."
)]
///
#[document_parameters("The closure to coerce.")]
///
#[document_returns("The closure wrapped in a `Box` as a trait object.")]
///
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// classes::*,
/// };
///
/// let f = <BoxBrand as ToDynFn>::new(|x: i32| x + 1);
/// assert_eq!(f(1), 2);
/// ```
fn new<'a, A: 'a, B: 'a>(f: impl 'a + Fn(A) -> B) -> Box<dyn 'a + Fn(A) -> B> {
Box::new(f)
}
/// Coerces a sized by-reference closure to a `dyn Fn(&A) -> B` wrapped in a `Box`.
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the closure.",
"The input type (the closure receives `&A`).",
"The output type of the function."
)]
///
#[document_parameters("The closure to coerce.")]
///
#[document_returns("The closure wrapped in a `Box` as a by-reference trait object.")]
///
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// classes::*,
/// };
///
/// let f = <BoxBrand as ToDynFn>::ref_new(|x: &i32| *x + 1);
/// assert_eq!(f(&1), 2);
/// ```
fn ref_new<'a, A: 'a, B: 'a>(f: impl 'a + Fn(&A) -> B) -> Box<dyn 'a + Fn(&A) -> B> {
Box::new(f)
}
}
}
#[cfg(test)]
mod tests {
use crate::{
brands::BoxBrand,
classes::{
Pointer,
ToDynFn,
to_dyn_fn::{
to_dyn_fn,
to_ref_dyn_fn,
},
},
};
#[test]
fn test_box_new() {
let ptr = <BoxBrand as Pointer>::new(42);
assert_eq!(*ptr, 42);
}
#[test]
fn test_box_to_dyn_fn() {
let f = <BoxBrand as ToDynFn>::new(|x: i32| x + 1);
assert_eq!(f(1), 2);
}
#[test]
fn test_box_to_dyn_fn_ref() {
let f = <BoxBrand as ToDynFn>::ref_new(|x: &i32| *x + 1);
assert_eq!(f(&1), 2);
}
#[test]
fn test_box_to_dyn_fn_free_fn() {
let f = to_dyn_fn::<BoxBrand, _, _>(|x: i32| x + 1);
assert_eq!(f(1), 2);
}
#[test]
fn test_box_to_ref_dyn_fn_free_fn() {
let f = to_ref_dyn_fn::<BoxBrand, _, _>(|x: &i32| *x + 1);
assert_eq!(f(&1), 2);
}
#[test]
fn test_box_not_clone() {
// Box<dyn Fn> is not Clone, confirming BoxBrand cannot implement RefCountedPointer.
let f = <BoxBrand as ToDynFn>::new(|x: i32| x + 1);
assert_eq!(f(1), 2);
// f.clone() would not compile
}
}