Enum Step 

pub enum Step<A, B> {
    Loop(A),
    Done(B),
}

Represents the result of a single step in a tail-recursive computation.

This type is fundamental to stack-safe recursion via MonadRec.

Type Parameters

• A: The “loop” type - when we return Loop(a), we continue with a.
• B: The “done” type - when we return Done(b), we’re finished.

Variants

• Loop(A): Continue the loop with a new value.
• Done(B): Finish the computation with a final value.

Examples

use fp_library::types::*;

let loop_step: Step<i32, i32> = Step::Loop(10);
let done_step: Step<i32, i32> = Step::Done(20);

Variants

Loop(A)

Continue the loop with a new value

Done(B)

Finish the computation with a final value

Implementations

impl<A, B> Step<A, B>

pub fn is_loop(&self) -> bool

Returns true if this is a Loop variant.

Type Signature

bool

Returns

true if the step is a loop, false otherwise.

Examples

use fp_library::types::*;

let step: Step<i32, i32> = Step::Loop(1);
assert!(step.is_loop());

pub fn is_done(&self) -> bool

Returns true if this is a Done variant.

Type Signature

bool

Returns

true if the step is done, false otherwise.

Examples

use fp_library::types::*;

let step: Step<i32, i32> = Step::Done(1);
assert!(step.is_done());

pub fn map_loop<C>(self, f: impl FnOnce(A) -> C) -> Step<C, B>

Maps a function over the Loop variant.

Type Signature

forall c. (A -> c) -> Step c B

Type Parameters

• C: The new loop type.

Parameters

• f: The function to apply to the loop value.

Returns

A new Step with the loop value transformed.

Examples

use fp_library::types::*;

let step: Step<i32, i32> = Step::Loop(1);
let mapped = step.map_loop(|x| x + 1);
assert_eq!(mapped, Step::Loop(2));

pub fn map_done<C>(self, f: impl FnOnce(B) -> C) -> Step<A, C>

Maps a function over the Done variant.

Type Signature

forall c. (B -> c) -> Step A c

Type Parameters

• C: The new done type.

Parameters

• f: The function to apply to the done value.

Returns

A new Step with the done value transformed.

Examples

use fp_library::types::*;

let step: Step<i32, i32> = Step::Done(1);
let mapped = step.map_done(|x| x + 1);
assert_eq!(mapped, Step::Done(2));

pub fn bimap<C, D>( self, f: impl FnOnce(A) -> C, g: impl FnOnce(B) -> D, ) -> Step<C, D>

Applies functions to both variants (bifunctor map).

Type Signature

forall c d. (A -> c, B -> d) -> Step c d

Type Parameters

• C: The new loop type.
• D: The new done type.

Parameters

• f: The function to apply to the loop value.
• g: The function to apply to the done value.

Returns

A new Step with both values transformed.

Examples

use fp_library::types::*;

let step: Step<i32, i32> = Step::Loop(1);
let mapped = step.bimap(|x| x + 1, |x| x * 2);
assert_eq!(mapped, Step::Loop(2));

Trait Implementations

impl<A: Clone, B: Clone> Clone for Step<A, B>

fn clone(&self) -> Step<A, B>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<A: Debug, B: Debug> Debug for Step<A, B>

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

Formats the value using the given formatter.

impl<A: Hash, B: Hash> Hash for Step<A, B>

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: PartialEq, B: PartialEq> PartialEq for Step<A, B>

fn eq(&self, other: &Step<A, B>) -> 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: Copy, B: Copy> Copy for Step<A, B>

impl<A: Eq, B: Eq> Eq for Step<A, B>

impl<A, B> StructuralPartialEq for Step<A, B>