A simple example of using Reader transformer to combine reader and future.

reader-t.js

const {tagged} = require('daggy');

// const
const K = (a) => (b) => a;

// Reader Transformer
module.exports = (M) => {
    const ReaderT = tagged('run');

    ReaderT.lift = (m) => ReaderT(K(m));

    ReaderT.of = ReaderT.prototype.of = (a) => {
        return ReaderT((e) => M.of(a));
    };

    ReaderT.ask = ReaderT((e) => M.of(e));

    ReaderT.prototype.chain = function(f) {
        return ReaderT((e) => {
            return this.run(e).chain((a) => f(a).run(e));
        });
    };

    ReaderT.prototype.map = function(f) {
        var m = this;
        return m.chain(a => m.of(f(a)))
    }

    return ReaderT;
};

readert_future.js

/**
 * This short program will encrypt the user password
 * and insert a new record into a mock database.
 */
const ReaderT = require('./lib/reader-t');
const Future = require('fluture');
const R = require('ramda');
const crypto = require('crypto');
const FutureReader = ReaderT(Future);

// our mock database
const database = [
  { email: '[email protected]', password: 'e0538fd8f022bb3b139d72cf12766cb0e31690ff' },
  { email: '[email protected]', password: '42c4fbf6fec201c66b82c97833b08d936d2cd526' }
]

// creates a statefull database connection
const connectTo = (db) => {
  return {
    insert: (doc) => Future.of(db.push(doc)),
    get: (i) => Future.of(db[i]),
    delete: (i) => Future.of(db.splice(i, 1)),
    list: () => Future.of(db)
  }
}

// some utility functions
const encrypt = (i) => crypto.createHash('sha1').update(i).digest('hex');
const encPassword = R.evolve({password: encrypt})


// utility function which makes it easier
// to ask for some dependency
// dependencies should reside in an object { dep: obj }
const inject = R.curry((dep, f, reader) => {
  return reader.chain((v) => {
    return FutureReader.ask.chain((env) => {
      return FutureReader.lift(f(env[dep], v));
    });
  });
});

// this is how you access the db connection inside the reader
const save = (db, user) => {
  return db.insert(user).chain(_ => db.list());
}

// the body of the program
const handler = R.pipe(
  R.map(encPassword),
  inject('db', FutureReader.lift(save)),
  R.map(R.map(R.dissoc('password')))
);

// this is our db connection now
const dbCon = connectTo(database);

const request = { email: '[email protected]', password: 'secret' };

const result = handler(FutureReader.of(request))
  .run({ 'db': dbCon }) // this is how you pass the db connection in
  .fork(console.error, console.log); // now fork the future