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//! By-reference variant of [`FunctorWithIndex`](crate::classes::FunctorWithIndex).
//!
//! **User story:** "I want to map over a memoized value by reference, with access to the index."
//!
//! ### Examples
//!
//! ```
//! use fp_library::{
//! brands::*,
//! classes::ref_functor_with_index::RefFunctorWithIndex,
//! types::*,
//! };
//!
//! let lazy = RcLazy::new(|| 42);
//! let mapped = <LazyBrand<RcLazyConfig> as RefFunctorWithIndex>::ref_map_with_index(
//! |_, x: &i32| x.to_string(),
//! &lazy,
//! );
//! assert_eq!(*mapped.evaluate(), "42");
//! ```
#[fp_macros::document_module]
mod inner {
use {
crate::{
classes::*,
kinds::*,
},
fp_macros::*,
};
/// By-reference mapping with index over a structure.
///
/// Similar to [`FunctorWithIndex`], but the closure receives `&A` instead of `A`.
/// This is the honest interface for memoized types like [`Lazy`](crate::types::Lazy)
/// that internally hold a cached `&A`.
#[kind(type Of<'a, A: 'a>: 'a;)]
pub trait RefFunctorWithIndex: RefFunctor + WithIndex {
/// Maps a function over the structure by reference, providing the index.
#[document_signature]
#[document_type_parameters(
"The lifetime of the values.",
"The type of the elements.",
"The type of the result."
)]
#[document_parameters(
"The function to apply to each element's index and reference.",
"The structure to map over."
)]
#[document_returns("The mapped structure.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// classes::ref_functor_with_index::RefFunctorWithIndex,
/// types::*,
/// };
///
/// let lazy = RcLazy::new(|| 42);
/// let mapped = <LazyBrand<RcLazyConfig> as RefFunctorWithIndex>::ref_map_with_index(
/// |_, x: &i32| x.to_string(),
/// &lazy,
/// );
/// assert_eq!(*mapped.evaluate(), "42");
/// ```
fn ref_map_with_index<'a, A: 'a, B: 'a>(
f: impl Fn(Self::Index, &A) -> B + 'a,
fa: &Self::Of<'a, A>,
) -> Self::Of<'a, B>;
}
/// Maps a function over a structure by reference with access to the index.
///
/// Free function version that dispatches to [the type class' associated function][`RefFunctorWithIndex::ref_map_with_index`].
#[document_signature]
#[document_type_parameters(
"The lifetime of the values.",
"The brand of the structure.",
"The type of the elements.",
"The type of the result."
)]
#[document_parameters(
"The function to apply to each element's index and reference.",
"The structure to map over."
)]
#[document_returns("The mapped structure.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::explicit::*,
/// types::*,
/// };
///
/// let lazy = RcLazy::new(|| 42);
/// let mapped =
/// map_with_index::<LazyBrand<RcLazyConfig>, _, _, _, _>(|_, x: &i32| x.to_string(), &lazy);
/// assert_eq!(*mapped.evaluate(), "42");
/// ```
pub fn ref_map_with_index<'a, Brand: RefFunctorWithIndex, A: 'a, B: 'a>(
f: impl Fn(Brand::Index, &A) -> B + 'a,
fa: &Brand::Of<'a, A>,
) -> Brand::Of<'a, B> {
Brand::ref_map_with_index(f, fa)
}
}
pub use inner::*;