menrva

Ambitious data-flow library.

Getting Started

Install the module with: npm install menrva

var menrva = require('menrva');
menrva.some('awe'); // some, as in awesome?

API

Signal

The core type of menrva. Signal is abstract class, and cannot be created explicitly.

Similar concepts are: Behaviours in FRP, Properties in bacon.js.

You can add methods to Signal's prototype. They will be available on all signals.

signal.map

map (@ : Signal a, f : a -> b, eq = egal : b -> b -> boolean) : Signal b

signal.onValue

onValue (@ : Signal a, callback : a -> void) -> Unsubscriber

Add value callback. callback is immediately executed with the current value of signal. After than callback will be called, each time signal's value changes.

The return value is a function, which will remove the callback if executed.

Source

A signal which value you can set.

Similar concepts are: Bacon.Model in bacon.js, BehaviourSubject in Rx.

source

source (initialValue : a, eq = egal : a -> a -> boolean) : Source a

source.set

set (@ : Source a, tx : Transaction, value : a) : void

source.modify

modify (@ : Source a, tx : Transaction, f : a -> a) : void

Mofify source value. f will be called with current value of signal inside the transaction.

Signal combinators

combine

combine (Signal a..., f : a... -> b) : Signal b

Applicative n-ary lift. Lift pure function to operate on signals:

var $sum = menrva.combine($a, $b, function (a, b) {
  return a + b;
});

Transaction

One gathers atomic updates into single transaction (to avoid glitches).

var tx = menrva.transaction();
sourceA.set(tx, 42);
sourceB.modify(tx, function (x) { return x + x; });
tx.commit(); // not necessary, transactions are auto-commited

There are also optional syntaxes for simple transactions:

menrva.transaction()
  .set(sourceA, 42)
  .modify(sourceB, function (x) { return x + x; })
  .commit();

or even

menrva.transaction([sourceA, 42, sourceB, function(x) { return x + x; }]).commit();

transaction

transaction (facts) : Transaction

Create transaction.

Shorthand syntax:

transaction ([sourceA, valueA, sourceB, valueB ...]) : Transaction

If value is function, source.modify(tx, value) is called; otherwise source.set(tx, value).

transaction.commit

Commit the transaction, forcing synchronous data propagation.

transaction.rollback

Rollback the transaction. Maybe be called multiple times (consecutives calls are no-op).

Note: for now rollback only resets the pending actions in transactions. Transaction is still valid, and more actions can be added

Lens

Lenses are composable functional references. They allow you to access and modify data potentially very deep within a structure!

source.zoom

zoom (@ : Source a, path : Path a b, eq = egal : b -> b -> boolean) : Source b

Zoom (or focus) into part specified by path of the original signal. One can set and modify zoomed signals, they act as sources.

var quux = source.zoom("foo.bar.quux");

Convinience methods

signal.log

signal.log (@ : Signal a, args...) : Unsubscriber

Essentially `signal.onValue(console.log.bind(console, args...))

signal.onSpread

signal.onSpread (@ : Signal [a, b...], callback : a -> b ... -> void) : Unsubscriber

onValue with signal's tuple arguments spread.

tuple

tuple (x : Signal a, y : Signal b...) : Signal [a, b...]

Combine signals into tuple.

Equalities

egal

egal (a, b) : boolean

Identity check. Object.is. http://wiki.ecmascript.org/doku.php?id=harmony:egal

Option

Also known as Maybe.

option.equals

equals (@ : option a, other : *, eq = eqal : a -> a -> boolean) : boolean

Equality check.

option.map

map (@ : option a, f : a -> b) : option b

option.elim

elim (@ : option a, x : b, f : a -> b) : b

option.orElse

orElse (@ : option a, x : a) : a

Contributing

In lieu of a formal styleguide, take care to maintain the existing coding style.

Add tests for any new or changed functionality. 100% coverage isn't hard. Semantic coverage is important too though.

Note: README.md is autogenerated file.

Release History

• 0.0.6 Convinience methods
• 0.0.5 Lens
• 0.0.4 Internal improvements
• 0.0.3 Slight changes in API
• 0.0.2 Basic data-flow functionality
• 0.0.1 Name reservation

License

Copyright (c) 2014 Oleg Grenrus. Licensed under the MIT license.