Function map_first 

pub fn map_first<'a, Brand: Kind_266801a817966495, A: 'a, B: 'a, C: 'a, FA, Marker>(
    f: impl MapFirstDispatch<'a, Brand, A, B, C, FA, Marker>,
    p: FA,
) -> <Brand as Kind_266801a817966495>::Of<'a, B, C>

Maps a function over the first type argument of a bifunctor.

Corresponds to lmap in both Haskell and PureScript.

Dispatches to either Bifunctor::map_first or RefBifunctor::ref_map_first based on the closure’s argument type.

The Marker and FA type parameters are inferred automatically by the compiler. Callers write map_first::<Brand, _, _, _, _>(...) and never need to specify Marker or FA explicitly.

Type Signature

forall Brand A B C. Bifunctor Brand => (A -> B, Brand A C) -> Brand B C

Type Parameters

• 'a: The lifetime of the values.
• Brand: The brand of the bifunctor.
• A: The type of the first value.
• B: The type of the first result.
• C: The type of the second value.
• FA: The container type (owned or borrowed), inferred from the argument.
• Marker: Dispatch marker type, inferred automatically.

Parameters

• f: The function to apply to the first value.
• p: The bifunctor value (owned for Val, borrowed for Ref).

Returns

A new bifunctor with the first value transformed.

Examples

use fp_library::{
	brands::*,
	functions::explicit::*,
};

// Owned
let x = Result::<i32, i32>::Err(5);
let y = map_first::<ResultBrand, _, _, _, _, _>(|e| e * 2, x);
assert_eq!(y, Err(10));

// By-ref
let x = Result::<i32, i32>::Err(5);
let y = map_first::<ResultBrand, _, _, _, _, _>(|e: &i32| *e * 2, &x);
assert_eq!(y, Err(10));