Struct Const 

pub struct Const<'a, R, A>(pub R, pub PhantomData<&'a A>);

The Const functor.

Const<R, A> stores a value of type R and ignores the type A.

Type Parameters

• 'a: The lifetime of the values.
• R: The stored type.
• A: The ignored type.

Tuple Fields

0: R

1: PhantomData<&'a A>

Implementations

impl<'a, R, A> Const<'a, R, A>

Type Parameters

• 'a: The lifetime of the values.
• R: The stored type.
• A: The ignored type.

pub fn new(r: R) -> Self

Creates a new Const instance.

Type Signature

forall R A. R -> Const R A

Parameters

• r: The value to store.

Returns

A new Const instance.

Examples

use fp_library::types::const_val::Const;

let c: Const<i32, String> = Const::new(42);
assert_eq!(c.0, 42);

pub fn map<B>(self, _f: impl FnOnce(A) -> B) -> Const<'a, R, B>

Maps over the phantom type parameter, preserving the stored value.

Since Const ignores its second type parameter, the function is never called. This is the inherent method form of Functor::map.

Type Signature

forall R A B. (Const R A, A -> B) -> Const R B

Type Parameters

• B: The new phantom type.

Parameters

• self: The Const instance.
• _f: The function to map (ignored).

Returns

A new Const instance with the same stored value but a different phantom type.

Examples

use fp_library::types::const_val::Const;

let c: Const<i32, String> = Const::new(42);
let mapped: Const<i32, bool> = c.map(|s: String| s.is_empty());
assert_eq!(mapped.0, 42);

pub fn lift2<B, C>( self, other: Const<'a, R, B>, _f: impl FnOnce(A, B) -> C, ) -> Const<'a, R, C>

where R: Semigroup,

Combines two Const values by appending their stored values, discarding the phantom types.

This is the inherent method form of Lift::lift2.

Type Signature

forall R A B C. Semigroup R => (Const R A, Const R B, (A, B) -> C) -> Const R C

Type Parameters

• B: The second phantom type.
• C: The result phantom type.

Parameters

• self: The Const instance.
• other: The other Const instance.
• _f: The function to lift (ignored).

Returns

A new Const instance with the appended stored values.

Examples

use fp_library::types::const_val::Const;

let c1: Const<String, i32> = Const::new("Hello".to_string());
let c2: Const<String, i32> = Const::new(" World".to_string());
let lifted = c1.lift2(c2, |a: i32, b: i32| a + b);
assert_eq!(lifted.0, "Hello World");

pub fn apply_first<B>(self, other: Const<'a, R, B>) -> Const<'a, R, A>

where R: Semigroup,

Combines the stored values of two Const instances, keeping the phantom type of the first.

This is the inherent method form of ApplyFirst::apply_first.

Type Signature

forall R A B. Semigroup R => (Const R A, Const R B) -> Const R A

Type Parameters

• B: The phantom type of the second Const instance.

Parameters

• self: The Const instance.
• other: The second Const instance.

Returns

A new Const instance with the appended stored values.

Examples

use fp_library::types::const_val::Const;

let c1: Const<String, i32> = Const::new("Hello".to_string());
let c2: Const<String, bool> = Const::new(" World".to_string());
let result = c1.apply_first(c2);
assert_eq!(result.0, "Hello World");

pub fn apply_second<B>(self, other: Const<'a, R, B>) -> Const<'a, R, B>

where R: Semigroup,

Combines the stored values of two Const instances, keeping the phantom type of the second.

This is the inherent method form of ApplySecond::apply_second.

Type Signature

forall R A B. Semigroup R => (Const R A, Const R B) -> Const R B

Type Parameters

• B: The phantom type of the second Const instance.

Parameters

• self: The Const instance.
• other: The second Const instance.

Returns

A new Const instance with the appended stored values.

Examples

use fp_library::types::const_val::Const;

let c1: Const<String, i32> = Const::new("Hello".to_string());
let c2: Const<String, bool> = Const::new(" World".to_string());
let result = c1.apply_second(c2);
assert_eq!(result.0, "Hello World");

pub fn pure(_a: A) -> Self

where R: Monoid,

Creates a Const with the monoidal identity, ignoring the given value.

This is the inherent method form of Pointed::pure.

Type Signature

forall R A. Monoid R => A -> Const R A

Parameters

• _a: The value to wrap (ignored).

Returns

A new Const instance with the empty value of the stored type.

Examples

use fp_library::types::const_val::Const;

let c: Const<String, i32> = Const::pure(42);
assert_eq!(c.0, "".to_string());

Trait Implementations

impl<'a, R: Clone, A> Clone for Const<'a, R, A>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a, R: Debug, A: Debug> Debug for Const<'a, R, A>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a, R: Default, A: Default> Default for Const<'a, R, A>

fn default() -> Const<'a, R, A>

Returns the “default value” for a type.

impl<'a, R: Hash, A: Hash> Hash for Const<'a, R, A>

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<'a, R: Ord, A: Ord> Ord for Const<'a, R, A>

fn cmp(&self, other: &Const<'a, R, A>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<'a, R: PartialEq, A: PartialEq> PartialEq for Const<'a, R, A>

fn eq(&self, other: &Const<'a, R, A>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a, R: PartialOrd, A: PartialOrd> PartialOrd for Const<'a, R, A>

fn partial_cmp(&self, other: &Const<'a, R, A>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, R: Copy, A> Copy for Const<'a, R, A>

impl<'a, R: Eq, A: Eq> Eq for Const<'a, R, A>

impl<'a, R, A> StructuralPartialEq for Const<'a, R, A>