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map_second

Function map_second 

Source
pub fn map_second<'a, Brand: Kind_266801a817966495, A: 'a, B: 'a, C: 'a, FA, Marker>(
    g: impl MapSecondDispatch<'a, Brand, A, B, C, FA, Marker>,
    p: FA,
) -> <Brand as Kind_266801a817966495>::Of<'a, A, C>
Expand description

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

Corresponds to rmap in both Haskell and PureScript.

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

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

§Type Signature

forall Brand A B C. Bifunctor Brand => (B -> C, Brand A B) -> Brand A 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 second value.
  • C: The type of the second result.
  • FA: The container type (owned or borrowed), inferred from the argument.
  • Marker: Dispatch marker type, inferred automatically.

§Parameters

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

§Returns

A new bifunctor with the second value transformed.

§Examples

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

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

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