https://github.com/simonrichardson/fantasy-environment

Library for creating environment which holds methods and properties.
https://github.com/simonrichardson/fantasy-environment

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Library for creating environment which holds methods and properties.

• Host: GitHub
• URL: https://github.com/simonrichardson/fantasy-environment
• Owner: SimonRichardson
• Created: 2013-10-29T16:02:27.000Z (about 11 years ago)
• Default Branch: master
• Last Pushed: 2016-02-05T10:48:12.000Z (over 8 years ago)
• Last Synced: 2024-08-08T15:47:26.357Z (3 months ago)
• Language: JavaScript
• Size: 7.81 KB
• Stars: 4
• Watchers: 4
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Fantasy Environment

![](https://raw.github.com/puffnfresh/fantasy-land/master/logo.png)

An environment holds methods and properties.

Methods are implemented as multi-methods, which allow a form of

*ad-hoc polymorphism*. Duck typing is another example of ad-hoc

polymorphism, but only allows a single implementation at a time, via

prototype mutation.

A method instance is a product of a name, a predicate and an

implementation:

```javascript

   var env = environment()

       .method(

           // Name

           'negate',

           // Predicate

           function(n) {

               return typeof n == 'number';

           },

           // Implementation

           function(n) {

               return -n;

           }

       );

   env.negate(100) == -100;

```

We can now override the environment with Some more implementations:

```javascript

   var env2 = env

       .method(

           'negate',

           function(b) {

               return typeof b == 'boolean';

           },

           function(b) {

               return !b;

           }

       );

   env2.negate(100) == -100;

   env2.negate(true) == false;

```

Environments are immutable; references to `env` won't see an

implementation for boolean. The `env2` environment could have

overwritten the implementation for number and code relying on `env`

would still work.

Properties can be accessed without dispatching on arguments. They

can almost be thought of as methods with predicates that always

return true:

```javascript

   var env = fantasy.environment()

       .property('name', 'Fantasy');

   env.name === 'Fantasy';

```

## Testing

### Library

Fantasy Environment uses [nodeunit](https://github.com/caolan/nodeunit) 

for all the tests and because of this there is currently an existing 

[adapter](test/lib/test.js) in the library to help with integration 

between nodeunit and Fantasy Environment.

### Coverage

Currently Fantasy Environment is using [Istanbul](https://github.com/gotwarlost/istanbul) 

for code coverage analysis; you can run the coverage via the following

command:

_This assumes that you have istanbul installed correctly._

```

istanbul cover nodeunit -- test/*.js

```

It should report that the total coverage is at 100% (branches at 80.95%) 

for the whole lib.