mech-emit

An emitter returns the next element from a source for each invocation of the emitter.

That source could be an array, hashtable, open socket, list, a range (like 1..6), etc. Emitter don't care. It just emits the next thing.

Example Usage

• Generating Sequences Using Emitters
• Javascript Map, Filter and Reduce Without Lambdas (Callbacks)

Emitters Library

This library contains a bunch of emitters.

See Mechanism Home for more information and other libraries.

Supported Mechanisms

• emitFromArr - Given an array, emitFromArr emits a single element at a time from the array.
• emitFromRange - Given a range, emitFromRange emits a single element from that range.

// TODO: Add emitters like

• emitSin - Emits a sine wave with range 0 to 1 of a frequency. Returned value is relative to the last emission.
• emitCos - Emits a cosine wave with range 0 to 1 of a frequency. Returned value is relative to the last emission.
• emitTriangle - Emits a triangle wave with range 0 to 1 of a frequency. Returned value is relative to the last emission.
• emitFib - Emit the Fibonacci sequence.

emitFromArr

Given an array, emitFromArr will continue to emit each element in the array. If no more elements are left, emitFromArr will emit undefined. If repeat is true, emitFromArr will start emitting the array from the beginning: never emitting undefined.

var em = m.emitFromArr([3,4,8]);
em.go // 1st time returns 3
em.go // 2nd time returns 3
em.go // 3rd time returns 8
em.go // 4th time returns undefined
// then undefined forever

var em = m.emitFromArr([7,2],true);
em.go // 1st time returns 7
em.go // 2nd time returns 2
em.go // 3rd time returns 7
em.go // 4th time returns 2
// ... forever

When set to true, the emitter will emit forever. Be careful when using with emitters mechanisms like loop and map.

emitFromRange

Given a min, max and (increment-)by, emitFromRange will emit the range. At the end of the range, emitFromRange will emit undefined. If repeat is true, emitFromRange will start emitting the range from the beginning.

var em = m.emitFromRange(2,6,2);
em.go // 1st time returns 2
em.go // 2nd time returns 4
em.go // 3rd time returns 6
em.go // 4th time returns undefined
// then undefined forever

var em = m.emitFromRange(8,5,-1);
em.go // 1st time returns 8
em.go // 2nd time returns 7
em.go // 3rd time returns 6
em.go // 4th time returns 5
em.go // 5th time returns undefined
// then undefined forever

And, you can emit from a HUGE range:

var em = m.emitFromRange(0,Infinity,1000)
em.go // 1st time return 0
em.go // 2nd time returns 1000
em.go // 3rd time returns 2000
// then foreverish

And let's make our by an emitter:

var em = m.emitFromRange(1,300,m.emitFromArr([3, -1, 4],true));
em.go; // returns 1
em.go; // returns 4
em.go; // returns 3
em.go; // returns 7
em.go; // returns 10
// forever repeating when we hit 300

Infinite Sized Maps!

Let's say you want to apply an algorithm to a range of data that has no bounds.

Using mechanisms, this is really easy:

var em = m.add(2, m.emitFromRange(0,Infinity,1000));
em.go // 1st time return 2
em.go // 2nd time returns 1002
em.go // 3rd time returns 2002
// then foreverish

Passing this into a mapping mechanism:

var emap = m.map(
  m.add(2, m.emitFromRange(0, Infinity, 1000))
);
 
emap.go // limited to 1000 elements

This will not loop forever because, internally, emitFromRange limits to the number of items map will attempt to traverse to 1000. This number can be set.

But really, who needs a map when you can turn any algorithm into a "mapping" algorithm by simply adding emitters to the algorithm.

Add can become an add mapping algorithm by providing an emitter to one of adds operands.

Interface Change Warning

TODO: We may change the interface of emit's optional repeat parameter. We may make it:

• repeat - will cause the emitter to repeat when it reaches the end of the items to emit.
• reverse - will cause the emitter to reverse what it emits starting at the end of the array.
• repeat-reverse - will cause the emitter to flip flop between emitting forward and then reverse.

Setup

Using In Your Projects

Change directory to your node project.

$ npm install --save mech-emit

Development

Get Involved!

There are a lot of core mechanisms just waiting to be created. Many of them can be created in a few hours including in-depth tests. Clone mech-library to get started!

Setup

Install:

$ npm install

Continuous test:

$ gulp

Test:

$ gulp webtests

Test Server

Read documentation in gulpfile.js to see how to setup automated web testing.

$ gulp webserver