Struct Writer 

pub struct Writer<W, A> {
    pub value: A,
    pub log: W,
}

A Writer monad: accumulates a log alongside a value.

Fields

value: A

The produced value.

log: W

The accumulated log.

Implementations

impl<W, A> Writer<W, A>

where W: IntoIterator + Clone + Default + Extend<W::Item>,

pub fn pure(a: A) -> Self

where W: Default,

Lift a pure value with an empty log.

impl<A> Writer<Vec<String>, A>

pub fn new(value: A, log: Vec<String>) -> Self

Create a writer with a value and initial log entries.

pub fn bind<B>( self, f: impl FnOnce(A) -> Writer<Vec<String>, B>, ) -> Writer<Vec<String>, B>

Monadic bind: combine logs.

pub fn fmap<B>(self, f: impl FnOnce(A) -> B) -> Writer<Vec<String>, B>

Map over the value.

pub fn tell(msg: String) -> Writer<Vec<String>, ()>

Emit a single log message.

pub fn into_log(self) -> Vec<String>

Return only the log.

pub fn into_value(self) -> A

Return only the value.

Trait Implementations

impl<W: Clone, A: Clone> Clone for Writer<W, A>

fn clone(&self) -> Writer<W, A>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<W: Debug, A: Debug> Debug for Writer<W, A>

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

Formats the value using the given formatter.