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6.2 Common

The (goblins actor-lib common) module provides actors wrapping functional data structures, allowing Goblins transactionality guarantees while providing an apparently mutable interface.

Constructor: ^seteq bcom initial … ¶

Construct an actor representing a set (each member is unique). A seteq has four methods:

• add val: Add val to the set.
• remove val: Remove val from the set.
• member? val: Return #t if val is in the set, else #f.
• as-list: Return a representation of the set as a Scheme list. Note that the order of items in the list is not specified.

> (define a-set (spawn ^seteq 'a 'b 'c))
> ($ a-set 'as-list)
=> (a b c)
> ($ a-set 'member? 'c)
=> #t
> ($ a-set 'member? 'f)
=> #f
> ($ a-set 'add 'f)
> ($ a-set 'remove 'b)
> ($ a-set 'as-list)
=> (f c a)

Constructor: ^ghash bcom [ht ghash-null] ¶

Construct an actor representing a hashtable using eq? for key lookup and equal? for other comparisons. ht, if provided, is the underlying ghash to use as the starting state. See (goblins ghash) module for the compatible hashtable implementation.

A ghash actor has five methods:

• ref key [dflt #f]: Return the value associated with key, or dflt if the key is not found.
• set key val: Add key to the ghash and associate it with val.
• has-key? key: Return #t if key is in the ghash; otherwise return #f.
• remove key: Delete key and its associated value from the ghash.
• data: Return the underlying ghash.

> (define ag (spawn ^ghash))
> ($ ag 'set "dog" "animal")
> ($ ag 'set "cesna" "plane")
> ($ ag 'data)
=> $<ghash (2)>
> ($ ag 'ref "cesna")
=> "plane"
> ($ ag 'has-key? "dog")
=> #t
> ($ ag 'remove "cesna")
> ($ ag 'ref "cesna")
=> #f
> ($ ag 'ref "cesna" 'missing)
=> missing
> ($ ag 'data)
=> $<ghash (1)>

Persistence Environment: common-env ¶