Object subclass: #SortedDirectory
  instanceVariableNames: 
    'associations '
  classVariableNames: ''
  poolDictionaries: ''   !


!SortedDirectory class methods !
 
new
        "comment"
    | answer |
    answer := super new.
    answer init.
    ^ answer.! !



!SortedDirectory methods !
  
associations

   ^associations!
   
display: aStream
        "Basic diagnostic contents to the Stream."
    associations do: [ :association | aStream nextPutAll: (association key). aStream tab. aStream nextPutAll: (association value). aStream cr. ].!

exists: k
        "Checks the existence of a certain key in the directory"
    associations findFirst: [ :association | (association key) = k ] ifAbsent: [ ^false ].
    ^true.!

init
        "Set up sorting criterion."
    associations := SortedCollection new.
    associations sortBlock: [:a :b | (a key) <= (b key)]!
 
lookup: k
        "Answers association with key k."
    (self exists: k)
        ifFalse: [ ^ nil ]
        ifTrue: [ ^ associations at: (associations findFirst: [ :association | k = (association key) ]) ].!
 
remove: k
        "removes association with key k"
    (self exists: k)
        ifTrue:     [ associations removeIndex: (associations findFirst: [ :association | k = (association key) ] ) ]
        ifFalse:   [ ]!
   
set: k value: v
        "Sets key to value if key already exists, otherwise create a new key and set."
    (self exists: k)    ifFalse:    [ associations add: ( Association key: k value: v ) ]
                               ifTrue:      [ self remove: k. self set: k value: v. ].! !