Keys and Parameters

The library offers a flexible and typesafe means to create Parameters to store values like primitive types, collection types or domain specific types.

A Parameter is a Key and Value where the Value must be from a set of defined primitive types including binary data. The Value of a Parameter is always considered to be an Array of the type (i.e. if a single value is stored it is at array location 0). A Parameter is immutable; a modification to an existing Parameter will return a new instance.

A Value can also have Units, which must be of the defined types. See Units for more information. At this time Units are informational only – no calculation or conversion support is provided. Some systems may provide a key value with different units, and receiver can inspect the Units to make a decision on how to handle the value.

A ParameterSet is a Set of Parameter. Various other message types include a ParameterSet (e.g. Setup, Event). A key is unique in a ParameterSet since it is a Set.

How to create a Parameter using the helper functions¶

• Choose an appropriate KeyType from the tables below.
• Calling the set method on KeyType helper and supplying a string keyName will return a suitably typed parameter instance.

Example snippets for creating parameter of simple, array and matrix type¶

Typescript

copysource
// primitives
const booleanParam: Parameter<BooleanKey> = booleanKey('flag').set([false])

const intParam: Parameter<IntKey> = intKey('RandomKeyName').set([123, 12432])
// intParam.keyName === 'RandomKeyName'
// intParam.keyTag === 'IntKey'
// intParam.values === [123, 12432]
// intParam.units === 'NoUnits' // default unit is `NoUnits`
// -------------

// arrays
const filterkey = intArrayKey('filter')
const filterParam: Parameter<IntArrayKey> = filterkey.set([
  [1, 2, 3],
  [4, 5, 6]
])
// -------------

// matrices
const positionMatrixKey = byteMatrixKey('positions', Units.meter)
const positions: Parameter<ByteMatrixKey> = positionMatrixKey.set([
  [
    [1, 2],
    [3, 4]
  ],
  [
    [5, 6],
    [7, 8]
  ]
])

Primitive Data types¶

Array Data types¶

Matrix Data types¶

Domain Specific Types¶

• choice : A key for a choice item similar to an enumeration

Example snippets for creating choice parameters¶

Typescript

copysource
// choice key

const choices = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'] as const

const weekDaysKey = choiceKey('weekDaysKey', choices)
const weekDayParam = weekDaysKey.set('Mon', 'Wed')
// weekDayParam === Parameter('weekDaysKey', 'ChoiceKey', ['Mon', 'Wed'], 'NoUnits')

// -------------

Coordinate Types¶

Example snippet for creating coordinate parameters¶

Typescript

copysource
const cometCoord = new CometCoord(
  new Tag('BASE'),
  2000,
  new Angle(324000000000),
  new Angle(7200000000),
  new Angle(360000000000),
  1.4,
  0.234
)
const cometParam: Parameter<CometCoordKey> = cometCoordKey('comet key', Units.degree).set([cometCoord])

//coord key is base trait of all coordinate key types.
const coordParam: Parameter<CoordKey> = coordKey('base coordinate').set([cometCoord])