Paths

A reference is a document of the kind ref. Its value is a path: a list that starts with a root of the context, then one step for each hop.

{ "type": "ref", "value": ["names", "cards", "ids", 1] }

The glyphs so far: 17, 2 new on this page

• 42Data: a value without a type
• number

  42
  A document: the tab is its type
• number

  42
  A dashed tab: the container declares the type
• add

  number

  1

  +

  number

  2
  Parts: a card inside a card
• kindA kind: a document of type kind
• OKDA rung: own, kind or default
• =3A port: the result of a document
• 0A sealed part: an evaluator cannot read it
• #NAME?An error value, in a red port
• numbera

  3
  A name tag: a binding for later steps
• ref

  namesa
  A reference: a path from a root of the context
• if

  test

  bool

  true

  =true

  then

  text

  “yes”

  =“yes”

  else

  text

  “no”

  not evaluated

  =“yes”
  Not evaluated: a part that its parent did not need
• ▸log

  text

  “hi”

  =“hi”

  =“hi”
  The run side: a magenta edge, and an effect
• 1log“hi”An effect: a numbered ticket in the world
• logA capability: an effect that a term can cause
• selfnamesThe five roots of a context: each path starts at onenew
• ref

  self

  nearest

  type“panel”

  width
  A computed step: a document with its own kindnew

Five roots

The context is a record with five roots. Each path starts at one of them.

Root	What it holds	Who sets it
self	The node that the term is part of	A node of a tree sets it for its parts
names	The values that the evaluators around the term bound	A sequence adds last and the name of each step
world	The registry of kinds	The host of the evaluation
event	The event that started a run	A handler
caps	The effects that the term can cause	Each evaluator gives the same set or a smaller set

The evaluators differ in how they change the context for their parts. The references do not differ: each reference is a walk from a root.

Each step is a question

A step does not carry a meaning of its own. The walk asks the thing that it reached: “what is this key on you?” The question goes up the ladder of the verb deref.

• Own: a node of a tree answers itself. It answers parent with the node that holds it, as any other field.
• Kind: a kind can name a deref evaluator for its documents.
• Default: a record answers with a field, and a list answers with an item.

A step can also be a document. Then the walker of its kind takes the step. nearest is such a kind: it follows parent until it reaches a node of a type. It is not special. It is a kind with an evaluator.

After each hop, the walk examines what it reached. When that is a reference, the walk follows it until it reaches something else. This is collapse. A cycle of references gives #CYCLE!.

ReferenceA nameUp a treeThe nearest panelA type is a pathA reference to a referenceA step that reaches nothing

The reference

ref

namescardsids1

The context: the walk starts at one of its five roots

selfnamesworldeventcaps

The hops

1. namesroot→{ cards, alias, real }
2. cardsdefault→ids[78]count2
3. idsdefault→[78]
4. 1default→8

The path reaches 8.

The root names holds the values that the evaluators around the reference bound. The default answers each later step: a field, then an item.

A type is a path too

The type of a document is a reference into the world: "add", or ["math", "product"]. A namespace groups kinds, and an alias is a reference to another kind. The walk follows an alias by collapse. A text or a list of keys in the field type is a base reference that the kernel resolves itself. Thus the chain of types stops there, and it does not expand forever.

The world of a sandbox is smaller. A path that the world cannot resolve gives #KIND?. Thus the reach of a term is what its world and its context can name.

Shorter forms are possible

A language on top of coeval can accept a shorter form, for example the text $parent.width. Its evaluator changes the short form into a path. The stored document always has the full path with its root, thus no reader guesses.