IBAFLang/IBAF-cbs/Funcons-beta/Values/Composite/Maps/index.md

layout, title, parent, ancestor

layout	title	parent	ancestor
default	Maps	Composite	Funcons-beta

Funcons-beta : Maps.cbs

Maps

[
  Type   maps
  Funcon map
  Funcon map-elements
  Funcon map-lookup    Alias lookup
  Funcon map-domain    Alias dom
  Funcon map-override
  Funcon map-unite
  Funcon map-delete
]

Meta-variables
  GT <: ground-values
  T? <: values?

Built-in Type
  maps(GT, T?)

maps(GT, T?) is the type of possibly-empty finite maps from values of type GT to optional values of type T?.

Built-in Funcon
  map(_:(tuples(GT, T?))*) : =>(maps(GT, T?))?

map(tuple(K1, V1?), ..., tuple(Kn, Vn?)) constructs a map from K1 to V1?, ..., Kn to Vn?, provided that K1, ..., Kn are distinct, otherwise the result is ( ).

Note that map(...) is not a constructor operation.

The built-in notation {K1|->V1?, ..., Kn|->Vn?} is equivalent to map(tuple(K1, V1?), ..., tuple(Kn, Vn?)). Note however that in general, maps cannot be identified with sets of tuples, since the values Vi? are not restricted to ground-values.

When T? <: types, maps(GT, T?) <: types. The type MT:maps(GT, T?) represents the set of value-maps MV:maps(GT, values?) such that dom(MV) is a subset of dom(MT) and for all K in dom(MV), map-lookup(MV, K) : map-lookup(MT, K).

Built-in Funcon
  map-elements(_:maps(GT, T?)) : =>(tuples(GT, T?))*

The sequence of tuples (tuple(K1, V1?), ..., tuple(Kn, Vn?)) given by map-elements(M) contains each mapped value Ki just once. The order of the elements is unspecified, and may vary between maps.

Assert
  map(map-elements(M)) == M

Built-in Funcon
  map-lookup(_:maps(GT, T?), K:GT) : =>(T?)?
Alias
  lookup = map-lookup

map-lookup(M,K) gives the optional value to which K is mapped by M, if any, and otherwise ( ).

Built-in Funcon
  map-domain(_:maps(GT, T?)) : =>sets(GT)
Alias
  dom = map-domain

map-domain(M) gives the set of values mapped by M.

map-lookup(M, K) is always ( ) when K is not in map-domain(M).

Built-in Funcon
  map-override(_:(maps(GT, T?))*) : =>maps(GT,T?)

map-override(...) takes a sequence of maps. It returns the map whose domain is the union of their domains, and which maps each of those values to the same optional value as the first map in the sequence in whose domain it occurs . When the domains of the M are disjoint, map-override(M) is equivalent to map-unite(M*).

Built-in Funcon
  map-unite(_:(maps(GT, T?))*) : =>(maps(GT, T?))?

map-unite(...) takes a sequence of maps. It returns the map whose domain is the union of their domains, and which maps each of those values to the same optional value as the map in the sequence in whose domain it occurs, provided that those domains are disjoint - otherwise the result is ( ).

Built-in Funcon
  map-delete(_:maps(GT, T?), _:sets(GT)) : =>maps(GT, T?)

map-delete(M, S) takes a map M and a set of values S, and returns the map obtained from M by removing S from its domain.

Assert
  map-domain(map-delete(M, S)) == set-difference(map-domain(M), S)

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