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2.1 Set Actions
set-action?
set-action
set-act
set-action-applicable?
set-action-requirements
set-action-obstructions
set-action-additions
set-action-deletions
set-action-cost
set-action-preconditions
set-action-postconditions
set-invariants
2.2 Set Conditions
set-condition?
set-condition
set-meets-condition?
set-condition-requirements
set-condition-obstructions
8.0

2 The Set State Representation

In the set state representation, the world is represented by a set. Actions and goals are represented by set actions and set conditions.

2.1 Set Actions

 (require planning/set/action) package: planning

A set action is an action in the set state representation.

procedure

(set-action? v)  boolean?

  v : any/c
A predicate for set actions.

procedure

(set-action [#:requirements requirements    
  #:obstructions obstructions    
  #:additions additions    
  #:deletions deletions    
  #:cost cost])  set-action?
  requirements : (sequence/c any/c) = empty-set
  obstructions : (sequence/c any/c) = empty-set
  additions : (sequence/c any/c) = empty-set
  deletions : (sequence/c any/c) = empty-set
  cost : (>=/c 0) = 1
Constructs a set action.

procedure

(set-act s action)  set?

  s : set?
  action : set-action?
Performs action on s. If action is not applicable in s, a contract error is raised.

Examples:
> (set-act (set 1 2 3)
           (set-action #:additions (set 10) #:deletions (set 2 3)))

(set 1 10)

> (set-act (set 1 2 3)
           (set-action #:requirements (set 5) #:additions (set 10)))

set-act: contract violation;

 The action must be applicable to the set.

      set: (set 1 2 3)

      action: (set-action #:additions (set 10) #:cost 1

#:deletions (set) #:obstructions (set) #:requirements (set

5))

  in: (->i

       ((set set?) (action set-action?))

       #:pre/name

       (set action)

       "The action must be applicable to the set."

       (set-action-applicable? action set)

       (_ set?))

  contract from:

      <pkgs>/planning/set/action.rkt

  blaming: top-level

   (assuming the contract is correct)

  at: <pkgs>/planning/set/action.rkt:7.3

procedure

(set-action-applicable? action s)  boolean?

  action : set-action?
  s : set?
Determines whether or not action is applicable in s: that is, whether or not s meets the action’s preconditions.

procedure

(set-action-requirements action)  set?

  action : set-action?
Returns the requirements of action.

procedure

(set-action-obstructions action)  set?

  action : set-action?
Returns the obstructions of action.

procedure

(set-action-additions action)  set?

  action : set-action?
Returns the additions of action.

procedure

(set-action-deletions action)  set?

  action : set-action?
Returns the deletions of action.

procedure

(set-action-cost action)  (>=/c 0)

  action : set-action?
Returns the cost of action.

procedure

(set-action-preconditions action)  set-condition?

  action : set-action?
Returns a set condition describing the preconditions of action.

procedure

(set-action-postconditions action)  set-condition?

  action : set-action?
Returns a set condition describing the postconditions of action.

Examples:
(define action
  (set-action
   #:requirements (set 1 3 5)
   #:additions (set 2 4)
   #:deletions (set 5)))

 

> (set-action-preconditions action)

(set-condition #:obstructions (set) #:requirements (set 1 3 5))

> (set-action-postconditions action)

(set-condition #:obstructions (set 5) #:requirements (set 1 2 3 4))

procedure

(set-invariants s actions)  set-condition?

  s : set?
  actions : (sequence/c set-action?)
Determines the invariants of s that is, the conditions that will always be true no matter what sequence of actions from actions are performed.

Examples:
> (set-invariants (set liquid) (set melt freeze))

(set-condition #:obstructions (set) #:requirements (set))

> (set-invariants (set solid liquid) (set evaporate condense))

(set-condition

 #:obstructions (set)

 #:requirements (set #<state-of-matter:solid>))

2.2 Set Conditions

 (require planning/set/condition) package: planning

A set condition is a condition in the set state representation. A set condition is a set of requirements and a set of obstructions. To meet a set condition, a set must contain all of the condition’s requirements and none of its obstructions.

procedure

(set-condition? v)  boolean?

  v : any/c
A predicate for set conditions.

procedure

(set-condition [#:requirements requirements    
  #:obstructions obstructions])  set-condition?
  requirements : (sequence/c any/c) = empty-set
  obstructions : (sequence/c any/c) = empty-set
Constructs a set condition.

procedure

(set-meets-condition? s condition)  boolean?

  s : set?
  condition : set-condition?
Determines whether or not s meets condition. To meet condition, s must contain all of the condition’s requirements and none of its obstructions.

Examples:
> (define primes (set 2 3 5 7 11))
> (set-meets-condition? primes (set-condition #:requirements (set 7 11)))

#t

> (set-meets-condition? primes (set-condition #:obstructions (set 2 4 6 8)))

#f

> (set-meets-condition? primes (set-condition #:obstructions (set 4 6 8)))

#t

procedure

(set-condition-requirements condition)  set?

  condition : set-condition?
Returns the requirements of condition.

procedure

(set-condition-obstructions condition)  set?

  condition : set-condition?
Returns the obstructions of condition.