"

 COPYRIGHT (c) 1991 by Claus Gittinger

              All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

Collection subclass:#Set

       classVariableNames:''

       poolDictionaries:''

       category:'Collections-Unordered'

!

Set comment:'

COPYRIGHT (c) 1991 by Claus Gittinger

              All Rights Reserved

a Set is a collection where each element occurs at most once.

written jun 91 by claus

jan 93 claus: changed to use hashing

'!

!Set class methodsFor:'instance creation'!

new

    "return a new empty Set"

    ^ self new:7

!

new:anInteger

    "return a new empty Set with space for anInteger elements"

    ^ self basicNew setTally:anInteger

! !

!Set methodsFor:'private'!

fullCheck

    "check if dictionary is full, grow if so.

     Definition of full is currently:'filled more than 70%'"

    "grow if filled more than 70% "

       self grow

    ]

!

goodSizeFor:arg

    "return a good array size for the given argument.

     Returns the next prime after arg"

    arg <= 7 ifTrue:[^ 7].

    arg <= 131072 ifTrue:[

           "2 4 8  16 32 64 128 256 512 1024 2048 4096 8192 16384 32768 65536 131072"

        ^ #(7 7 11 17 37 67 131 257 521 1031 2053 4099 8209 16411 32771 65537 131101) at:(arg highBit)

    ].

    ^ arg bitOr:1

!

setTally:count

    "initialize the contents array (for at least count slots) 

     and set tally to zero.

     The size is increased to the next prime for better hashing behavior."

    tally := 0

!

find:key ifAbsent:aBlock

    "Look for the key in the receiver.  If it is found, return

     the index of the slot containing the key, otherwise

     return the value of evaluating aBlock."

    |index      "{ Class:SmallInteger }"

     length startIndex probe|

    startIndex := key hash \\ length + 1.

    index := startIndex.

    [true] whileTrue:[

        key = probe ifTrue:[^ index].

        index == length ifTrue:[

            index := 1

        ] ifFalse:[

            index := index + 1

        ].

    ]

!

    "Look for the key in the receiver.  If it is found, return

     the index of the slot containing the key, otherwise

     return the index of the first unused slot. Grow the receiver,

     if key was not found, and no unused slots where present"

    |index      "{ Class:SmallInteger }"

     length startIndex probe|

    startIndex := key hash \\ length + 1.

    index := startIndex.

    [true] whileTrue:[

        (probe isNil or: [key = probe]) ifTrue:[^ index].

        index == length ifTrue:[

            index := 1

        ] ifFalse:[

            index := index + 1

        ].

    ]

!

findNil:key

    "Look for the next slot usable for key.  This method assumes that

     key is not already in the receiver - used only while growing/rehashing"

    |index  "{ Class:SmallInteger }"

     length|

    index := key hash \\ length + 1.

        index == length ifTrue:[

            index := 1

        ] ifFalse:[

            index := index + 1

        ].

        "notice: no check for no nil found - we must find one since

         this is only called after growing"

    ].

    ^ index

!

grow

    "change the number of element slots of the collection to a useful

     new size"

!

grow:newSize

    "change the number of element slots of the collection - to do this,

     we have to rehash (which is done by re-adding all elements to a new

     empty set)."

        elem notNil ifTrue:[

            "cannot be already there"

        ].

!

rehash

    "rehash is done by re-adding all elements to a new empty set."

    | oldArray element 

      n "{ Class:SmallInteger }" |

    n := oldArray size.

    1 to:n do:[:index |

        element := oldArray at:index.

        element notNil ifTrue:[

            "cannot be already there"

        ].

    ]

!

rehashFrom:startIndex

    "rehash elements starting at index - after a remove"

    |element i "{ Class:SmallInteger }"

     length

     index "{ Class:SmallInteger }" |

    index := startIndex.

    [element notNil] whileTrue:[

        i := self findNil:element.

        i == index ifTrue:[

            ^ self

        ].

        index == length ifTrue:[

            index := 1

        ] ifFalse:[

            index := index + 1.

        ].

    ]

! !

!Set methodsFor:'accessing'!

at:index

    "report an error: at: is not allowed for Sets"

    ^ self errorNotKeyed

!

at:index put:anObject

    "report an error: at:put: is not allowed for Sets"

    ^ self errorNotKeyed

! !

!Set methodsFor:'testing'!

size

    "return the number of set elements"

    ^ tally

!

includes:anObject

    "return true if the argument anObject is in the receiver"

    ^ (self find:anObject ifAbsent:[0]) ~~ 0

!

isEmpty

    "return true if the receiver is empty"

    ^ tally == 0

!

occurrencesOf:anObject

    "return the number of occurrences of anObject in the receiver"

    (self find:anObject ifAbsent:[0]) == 0 ifTrue:[^ 0].

    ^ 1

!

isFixedSize

    "return true if the receiver cannot grow - this will vanish once

     Arrays and Strings learn how to grow ..."

    ^ false

! !

!Set methodsFor:'adding & removing'!

add:anObject

    "add the argument, anObject to the receiver"

    |index|

    anObject notNil ifTrue:[

            tally := tally + 1.

            self fullCheck.

        ]

    ].

    ^ anObject

!

remove:oldObject ifAbsent:exceptionBlock

    "remove oldObject from the collection and return it.

     If it was not in the collection return the value of exceptionBlock."

    |index next|

    index := self find:oldObject ifAbsent:[^ exceptionBlock value].

    tally := tally - 1.

    tally == 0 ifTrue:[

    ] ifFalse:[

            next := 1

        ] ifFalse:[

            next := index + 1.

        ].

        "this check is redundant - is also done in rehashFrom:,

         however, since there is some probability that the next

         element is nil, this saves a send sometimes

        "

            self rehashFrom:next.

        ]

    ].

    ^ oldObject

! !

!Set methodsFor:'enumerating'!

do:aBlock

    "perform the block for all members in the collection."

        each notNil ifTrue:[

            aBlock value:each

        ]

    ]

! !

!Set methodsFor: 'binary storage'!

readBinaryContentsFrom: stream manager: manager

    "must rehash after reload"

    super readBinaryContentsFrom: stream manager: manager.

    self rehash

! !