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//! Combining two by-ref contexts, keeping the first value, with [`ref_apply_first`].
//!
//! This is the by-ref counterpart of [`ApplyFirst`](crate::classes::ApplyFirst).
//!
//! ### Examples
//!
//! ```
//! use fp_library::{
//! brands::*,
//! functions::{
//! explicit::apply_first,
//! *,
//! },
//! types::*,
//! };
//!
//! let x = RcLazy::pure(3);
//! let y = RcLazy::pure(4);
//! let result = apply_first::<LazyBrand<RcLazyConfig>, _, _, _, _>(&x, &y);
//! assert_eq!(*result.evaluate(), 3);
//! ```
#[fp_macros::document_module]
mod inner {
use {
crate::kinds::*,
fp_macros::*,
};
/// A type class for combining two by-ref contexts, keeping the first value.
///
/// Requires `A: Clone` because the closure receives `&A` and must produce
/// an owned `A`. The default implementation uses [`RefLift::ref_lift2`](crate::classes::RefLift::ref_lift2).
#[kind(type Of<'a, A: 'a>: 'a;)]
pub trait RefApplyFirst: crate::classes::RefLift {
/// Combines two contexts, keeping the value from the first.
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the values.",
"The type of the value in the first context. Must be `Clone`.",
"The type of the value in the second context."
)]
///
#[document_parameters("The first context.", "The second context.")]
///
#[document_returns("A new context containing the value from the first context.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// classes::*,
/// types::*,
/// };
///
/// let x = RcLazy::pure(3);
/// let y = RcLazy::pure(4);
/// let result = LazyBrand::<RcLazyConfig>::ref_apply_first(&x, &y);
/// assert_eq!(*result.evaluate(), 3);
/// ```
fn ref_apply_first<'a, A: Clone + 'a, B: 'a>(
fa: &Apply!(<Self as Kind!( type Of<'a, T: 'a>: 'a; )>::Of<'a, A>),
fb: &Apply!(<Self as Kind!( type Of<'a, T: 'a>: 'a; )>::Of<'a, B>),
) -> Apply!(<Self as Kind!( type Of<'a, T: 'a>: 'a; )>::Of<'a, A>) {
Self::ref_lift2(|a: &A, _: &B| a.clone(), fa, fb)
}
}
/// Blanket implementation of [`RefApplyFirst`].
#[document_type_parameters("The brand type.")]
impl<Brand: crate::classes::RefLift> RefApplyFirst for Brand {}
/// Combines two contexts, keeping the value from the first.
///
/// Free function version that dispatches to [the type class' associated function][`RefApplyFirst::ref_apply_first`].
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the values.",
"The brand of the context.",
"The type of the value in the first context. Must be `Clone`.",
"The type of the value in the second context."
)]
///
#[document_parameters("The first context.", "The second context.")]
///
#[document_returns("A new context containing the value from the first context.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::{
/// explicit::apply_first,
/// *,
/// },
/// types::*,
/// };
///
/// let x = RcLazy::pure(3);
/// let y = RcLazy::pure(4);
/// let result = apply_first::<LazyBrand<RcLazyConfig>, _, _, _, _>(&x, &y);
/// assert_eq!(*result.evaluate(), 3);
/// ```
pub fn ref_apply_first<'a, Brand: RefApplyFirst, A: Clone + 'a, B: 'a>(
fa: &Apply!(<Brand as Kind!( type Of<'a, T: 'a>: 'a; )>::Of<'a, A>),
fb: &Apply!(<Brand as Kind!( type Of<'a, T: 'a>: 'a; )>::Of<'a, B>),
) -> Apply!(<Brand as Kind!( type Of<'a, T: 'a>: 'a; )>::Of<'a, A>) {
Brand::ref_apply_first(fa, fb)
}
}
pub use inner::*;