"

 COPYRIGHT.

 The above file is a Manchester Goodie protected by copyright.

 These conditions are imposed on the whole Goodie, and on any significant

 part of it which is separately transmitted or stored:

	* You must ensure that every copy includes this notice, and that

	  source and author(s) of the material are acknowledged.

	* These conditions must be imposed on anyone who receives a copy.

	* The material shall not be used for commercial gain without the prior

	  written consent of the author(s).

 Further information on the copyright conditions may be obtained by

 sending electronic mail:

	To: goodies-lib@cs.man.ac.uk

	Subject: copyright

 or by writing to The Smalltalk Goodies Library Manager, Dept of

 Computer Science, The University, Manchester M13 9PL, UK

 (C) Copyright 1992 University of Manchester

 For more information about the Manchester Goodies Library (from which 

 this file was distributed) send e-mail:

	To: goodies-lib@cs.man.ac.uk

	Subject: help 

"

Collection subclass:#Iterator

	instanceVariableNames:'block'

	classVariableNames:''

	poolDictionaries:''

	category:'Collections-Sequenceable'

!

Iterator comment:'An Iterator is a read-only collection that evaluates a block to yield the elements

 of the collection.'!

!Iterator class methodsFor:'documentation'!

copyright

"

 COPYRIGHT.

 The above file is a Manchester Goodie protected by copyright.

 These conditions are imposed on the whole Goodie, and on any significant

 part of it which is separately transmitted or stored:

	* You must ensure that every copy includes this notice, and that

	  source and author(s) of the material are acknowledged.

	* These conditions must be imposed on anyone who receives a copy.

	* The material shall not be used for commercial gain without the prior

	  written consent of the author(s).

 Further information on the copyright conditions may be obtained by

 sending electronic mail:

	To: goodies-lib@cs.man.ac.uk

	Subject: copyright

 or by writing to The Smalltalk Goodies Library Manager, Dept of

 Computer Science, The University, Manchester M13 9PL, UK

 (C) Copyright 1992 University of Manchester

 For more information about the Manchester Goodies Library (from which 

 this file was distributed) send e-mail:

	To: goodies-lib@cs.man.ac.uk

	Subject: help 

"

!

documentation

"

    Occasionally you may have a block that when evaluated can be

    treated as a collection -- i.e. it takes another block as parameter,

    then applies that to a sequence of values.

    This goodie wraps the block into an object -- an iterator -- which is

    part of the collection hierarchy, and therefore inherits a variety of

    useful collection-related methods.

    [info:]

	NAME            Iterator

	AUTHOR          miw@cs.man.ac.uk (Mario Wolczko)

	FUNCTION        a wrapper for blocks that iterate over collections

	ST-VERSION      4.0 4.1

	PREREQUISITES   

	CONFLICTS

	DISTRIBUTION    world

	VERSION         1

	DATE    18 Jun 1991

	SUMMARY

    [organisation:]

	Dept. of Computer Science   Internet:      mario@cs.man.ac.uk

	The University              uucp:        uknet!!!!man.cs!!!!mario

	Manchester M13 9PL          JANET:         mario@uk.ac.man.cs

	U.K.                        Tel: +44-61-275 6146  (FAX: 6236)

	______the mushroom project___________________________________

    [author:]

	Mario Wolczko miw@cs.man.ac.uk

"

!

examples

"

 an iterator, simulating a collection of 100 random values:

									[exBegin]

     |i b|

     b := [:whatToDo |

	       |rnd|

	       rnd := Random new.

	       1 to:100 do:[:i | 

		  whatToDo value:(rnd next)

	       ] 

	  ].

     i := Iterator on:b.

     i do:[:j |

	j printNL

     ].

									[exEnd]

 an iterator, simulating a collection of the lines

 in a file:

									[exBegin]

     |i b|

     b := [:whatToDo |

	       |s line|

	       s := 'smalltalk.rc' asFilename readStream.

	       [s atEnd] whileFalse:[

		  line := s nextLine.

		  whatToDo value:line.

	       ].

	       s close

	  ].

     i := Iterator on:b.

     i do:[:j |

	j printNL

     ].

									[exEnd]

"

! !

!Iterator class methodsFor:'instance creation'!

on: aBlock

    ^ self new block: aBlock

    "

     |i b|

     b := [:whatToDo | 

	       1 to:10 do:[:i | 

		  whatToDo value:i

	       ] 

	  ].

     i := Iterator on:b.

     i do:[:j |

	j printNL

     ].

    "

    "

     an iterator, simulating a collection of 100 random values:

     |i b|

     b := [:whatToDo |

	       |rnd|

	       rnd := Random new.

	       1 to:100 do:[:i | 

		  whatToDo value:(rnd next)

	       ] 

	  ].

     i := Iterator on:b.

     i do:[:j |

	j printNL

     ].

    "

    "Modified: 9.5.1996 / 14:26:49 / cg"

!

on:collection msg:msg

    ^ self new block: [ :aBlock | collection perform: msg with: aBlock]

    "

     |rnd i|

     rnd := Random new.

     i := Iterator on:[:a | rnd next].

     i do:[:j |

	j printNL

     ].

    "

    "Modified: 9.5.1996 / 14:21:40 / cg"

! !

!Iterator methodsFor:'accessing'!

identityIndexOf: anElement 

    "Answer the identity index of anElement within the receiver.  

     If the receiver does not contain anElement, answer 0."

    ^self identityIndexOf: anElement ifAbsent: [0]

!

identityIndexOf: anElement ifAbsent: exceptionBlock 

    "Answer the identity index of anElement within the receiver.  

     If the receiver does not contain anElement, answer the result 

     of evaluating the exceptionBlock."

    | index |

    index := 1.

    self do: [ :el | el == anElement ifTrue: [^index].  index := index + 1].

    ^exceptionBlock value

!

indexOf: anElement 

    "Answer the index of anElement within the receiver.  If the receiver does

    not contain anElement, answer 0."

    ^self indexOf: anElement ifAbsent: [0]

!

indexOf: anElement ifAbsent: exceptionBlock 

    "Answer the index of anElement within the receiver.  If the receiver does

    not contain anElement, answer the result of evaluating the exceptionBlock."

    | index |

    index := 1.

    self do: [ :el | el = anElement ifTrue: [^index].  index := index + 1].

    ^exceptionBlock value

! !

!Iterator methodsFor:'adding & removing'!

add: anObject

    "Iterators are read-only"

    self shouldNotImplement

!

remove: oldObject ifAbsent: anExceptionBlock 

    "Iterators are read-only."

    self shouldNotImplement

! !

!Iterator methodsFor:'converting'!

asOrderedCollection

    "Answer a new instance of OrderedCollection whose elements are the elements of

    the receiver.  The order in which elements are added depends on the order in

    which the receiver enumerates its elements.  In the case of unordered collections,

    the ordering is not necessarily the same for multiple requests for the conversion."

    | anOrderedCollection |

    anOrderedCollection := OrderedCollection new.

    self do: [:each | anOrderedCollection addLast: each].

    ^anOrderedCollection

! !

!Iterator methodsFor:'enumerating'!

do: aBlock

    block value: aBlock

!

findFirst: aBlock

    "Answer the index of the first element of the receiver

    for which aBlock evaluates as true."

    | index |

    index := 1.

    self do: [ :el | (aBlock value: el) ifTrue: [^index].  index := index + 1].

    ^0

!

findLast: aBlock

    "Answer the index of the last element of the receiver

    for which aBlock evaluates as true."

    | index last |

    index := 1.

    last := 0.

    self do: [ :el | (aBlock value: el) ifTrue: [last := index].  index := index + 1].

    ^last

!

keysAndValuesDo: aBlock  

    "Evaluate aBlock with each of the receiver's key/value pairs

    (e.g. indexes and elements) as the arguments."

    | index |

    index := 1.

    self do: [:el | aBlock value: index value: el.  index := index + 1]

! !

!Iterator methodsFor:'private'!

block: aBlock

    block := aBlock

!

species

    ^OrderedCollection

! !

!Iterator class methodsFor:'documentation'!

version

! !