akh

Akh

Javascript Monad and Monad Transformer Collection

Overview

Collection of simple monad and monad transformers that implement Fantasy Land's interfaces.

Links

• Documentation - Documentation of general interfaces and specific types.

Quick Example

Example is in Khepri but regular js works fine too.

with
    import 'akh::list' List,
    import 'akh::trans::state' StateT
in {

// Define a new monad using the state transformer on the list monad.
var M = StateT (List);

var run = StateT.runStateT \>> List.runList;

// Create a stateful computation
var c =
    M.of(1) // simple value
    
        // modify State
        .chain(\x ->
            M.modify \ s -> s + x + 'xyz')
        
        // Branch states
        .concat(
             M.put('new_state').map(\ -> 3),
             M.of 10,
             M.get // get the current state)
         
         // And operate on them
         .map(_ +, 'aa');

// Run the computation to get list of state value pairs
run(c, 'initial_state');
[
    {'x': '1aa', 's': 'state1xyz'},
    {'x': '3aa', 's': 'new_state'},
    {'x': '10aa', 's': 'state1xyz'}
    {'x': 'state1xyzaa', 's': 'state1xyz'}
]
}

Install

Node

Node files live in dist_node

$ npm install akh

With AMD

Node files live in dist

requirejs.config({
    paths: {
        'akh': './dist'
    }
});

require(['akh/list'], function(List) {
    ...
});

Included Types

Monad Transformers

• IdentityT - akh::trans::identity - Transforms a monad to itself. (Monad, Functor, Applicative Functor)
• StateT - akh::trans::state - State transformer. (Monad, Monoid, Functor, Applicative Functor)
• ListT - akh::trans::list - List transformer. (Monad, Monoid, Functor, Applicative Functor)
• ContT - akh::trans::cont - Continuation transformer. (Monad, Functor, Applicative Functor)
• DContT - akh::trans::dcont - Delimited continuation transformer. (Monad, Functor, Applicative Functor)
• EitherT - akh::trans::either - Either transformer. (Monad, Monoid, Functor, Applicative Functor)
• ErrorT - akh::trans::error - Error transformer. (Monad, Monoid, Functor, Applicative Functor)
• UniqueT - akh::unique Add unique int to monad (Monad, Monoid, Functor, Applicative Functor)

Monads

• Identity - akh::identity - Identity computation. (Monad, Functor, Applicative Functor)
• State - akh::state - Stateful computation. (Monad, Functor, Applicative Functor)
• List - akh::list - List computation. (Monad, Monoid, Functor, Applicative Functor)
• Cont - akh::cont - Continuation computation. (Monad, Functor, Applicative Functor)
• DCont - akh::dcont - Delimited continuation computation. (Monad, Functor, Applicative Functor)
• EitherT - akh::either - Either computation. (Monad, Functor, Applicative Functor)
• ErrorT - akh::error - Error computation. (Monad, Functor, Applicative Functor)
• Trampoline - akh::trampoline Trampolined computation (Monad, Functor, Applicative Functor)
• Unique - akh::unique Get Unique int (Monad, Monoid, Functor, Applicative Functor)

Contribute

Improvement and additions to Akh are welcome. Please report any issues or send a pull request.

Code

Akh is written in Khepri. Khepri is an ECMAScript derived language focused on functional programming that compiles to Javascript. Khepri sources are in lib directory with node output in dist_node and AMD output in dist.

# install khepri
$ npm install -g khepri

# Compile all Khepri files
$ npm run build

# Run tests
$ npm test

# While developing, auto compile changed files
$ khepri -w lib -o dist_node --package_manager=node

Changelog

1.1.0 - April 3, 2014

• Added base::liftA and base::liftA2 to lift to an applicative.
• Added derived applicative operation ac that curries f with the argument a.