data.these

data.these

This is a javascript adaptation of the haskell package these which provides a data structure containing either a value a or a value b or both, values a and b :

data These a b = This a
               | That b
               | These a b

API

Constructors

var t = These.This(1)
t instanceof These // => true

Creates an instance containing the this value 1.

var t = These.That(2)
t instanceof These // => true

Creates an instance containing the that value 2.

var t = These(1, 2)
t instanceof These // => true

Creates an instance containg the this value 1 and that value 2.

isThis

These.This(1).isThis // => true
These.That(1).isThis // => false
These.These(1).isThis // => false

The isThis property is true for This instances and false otherwise.

isThat

These.This(1).isThat // => false
These.That(1).isThat // => true
These.These(1).isThat // => false

The isThat property is true for That instances and false otherwise.

isThese

These.This(1).isThese // => false
These.That(1).isThese// => false
These.These(1).isThese // => true

The isThese property is true for These instances and false otherwise.

get

These.This('foo').get() // => 'foo'
These.That('bar').get() // => 'bar'
These.These('foo', 'bar') // => { _this: 'foo', _that: 'bar' }

The get function returns the wrapped value(s). In case of These the values are wrapped in an object.

these

These.This(val).these(f, g, h) // => f(val)
These.That(val).these(f, g, h) // => g(val)
These.These(val).these(f, g, h) // => h(val)

The these function accepts 3 functions - one for each case - and applies the correct function to the wrapped value.

fromThese

These.This('today').fromThese('sometime', 'somewhere') // => [ 'today', 'somewhere' ]
These.That('beijing').fromThese('sometime', 'somewhere') // => [ 'sometime', 'beijing' ]
These.These('today', 'beijing').fromThese('sometime', 'somewhere') // => [ 'today', 'beijing' ]

The these function accepts two values as default values and combines them with the value(s) provided by the These instance.

merge

var add = function(x,y) { return x + y };
These.This(1).merge(add) // => 1
These.That(1).merge(add) // => 1
These.These(1,2).merge(add) // => 3

The merge function accepts a binary to combine values from These instances. The wrapped value is returned as-is for This and That.

mapThese

var inc = function(x) { return x + 1 };
var dec = function(x) { return x - 1 };
These.This(1).mapThese(inc, dec) // => This { 2 }
These.That(2).mapThese(inc, dec) // => That { 1 }
These.These(1, 2).mapThese(inc, dec) // => These { 2, 1 }

The mapThese acts as a bi-functor accepting two functions, which are applied accordingly.

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