Akh Javascript Monad Library
Writer Monad and Monad Transformer forThe WriterT transformer, WriterT
, adds error control to a monad. The base type, Writer
, provides error logic on its own.
# To use as standalone package $ npm install --save akh.writer # To use as part of akh library $ npm install --save akh
Usage
WriterT
and Writer
implement the Fantasy Land monad, functor, and applicative functor interfaces.
// Writer monadWriterWriter // Writer monad transformerWriterTWriterT
Writer.run(m, w)
, m.run(w)
Perform a writer computation m
without output monoid w
and return { value, output}
WriterT.run(t, w)
, t.run(w)
Same as Writer.run
but for a monad transformer. Returns an Writer
value inside of the inner monad.
Writer.exec(m, w)
, m.exec(w)
Perform a writer computation m
without output monoid w
and return resulting value
Writer Interface
Writer.tell(b)
WriterT(M).tell(b)
Append b
to the output.
Writer ) === value: 4 output: List of 'output1'
Writer.listen()
WriterT(M).listen()
Produces the current value output pair as { value, output }
m.pass()
t.pass()
Exec current monad which returns a [value, f]
, then modify current output with f
and return value
.
m.censor(f)
t.censor(f)
Exec current monad, then modify current output with f
and return original value
.
Contributing
Contributions are welcome.
To get started:
$ cd akh-writer$ npm install # install dev packages $ npm test # run tests