.TH "sequence" 3 "Oct 12, 2003"
.SH Sequence
.PP
.B
Inherits from:

Object
.SH Class Description
.PP
Sequences are used to loop or 
.I
sequence
over a group of objects\&.  Typically, an 
.B
Sequence
instance is generated by using some method like 
.B
OrdCltn
\&'s 
.B
eachElement
\&.  Then, within a loop, one can send 
.B
next
messages to the sequence until the end is reached (when the 
.B
next
method returns 
.B
nil
)\&.  Finally, after using the sequence, you have to free the sequence object\&.
.SH Warning
.PP
Using a sequence can lead to problems if, in sequencing over a collection, that collection is modified, e\&.g\&., as in the following :
.RS 3

id item;
.br
id aSeq;
.br

.br
aSeq = [aCol eachElement];
.br
while ((item = [aSeq next])) [aCol add:something]; /* WRONG !!! */
.br
aSeq = [aSeq free];
.br

.RE
.PP
You may not modify a group of objects while sequencing over its contents\&.
.SH Method types
.PP 
.B
Creation
.RS 3
.br
* copy
.br
* free
.RE
.PP 
.B
Interrogation
.RS 3
.br
* size
.RE
.PP 
.B
Accessing
.RS 3
.br
* next
.br
* peek
.br
* previous
.br
* first
.br
* last
.RE
.PP 
.B
Printing
.RS 3
.br
* printOn:
.RE
.PP 
.B
Performing
.RS 3
.br
* do:
.RE
.SH Methods
.PP 
copy
.RS 1
-
.B
copy
.RE
.PP
Returns a copy of the sequence\&.  Can be used independently of the original sequence\&.
.PP 
free
.RS 1
-
.B
free
.RE
.PP
Frees the receiver, but not the objects in the collection being sequenced over\&.
.PP 
size
.RS 1
- (
unsigned
)
.B
size
.RE
.PP
Returns the total number of items in the sequence\&.
.PP 
next
.RS 1
-
.B
next
.RE
.PP
Returns the next object in the sequence if there is one and advances the sequence\&.  When it reaches the end of the sequence, returns 
.B
nil
\&.
.PP 
peek
.RS 1
-
.B
peek
.RE
.PP
Returns the next object in the sequence if there is one, but does not advance the sequence\&.  When it reaches the end of the sequence, returns 
.B
nil
\&.
.PP 
previous
.RS 1
-
.B
previous
.RE
.PP
Returns the object that was returned by the last 
.B
next
message\&.  If there were no 
.B
next
messages since the sequence was created, or the sequence is empty, returns 
.B
nil
\&.  Doesn\&'t affect the current position in the sequence\&.
.PP 
first
.RS 1
-
.B
first
.RE
.PP
Returns the first object in the sequence, unlesss there are no members in the sequence, in which case it returns 
.B
nil
\&.  Doesn\&'t affect the current position in the sequence\&.
.PP 
last
.RS 1
-
.B
last
.RE
.PP
Returns the last object in the sequence, unlesss there are no members in the sequence, in which case it returns 
.B
nil
\&.  Doesn\&'t affect the current position in the sequence\&.
.PP 
printOn:
.RS 1
-
.B
printOn
:(IOD)
.I
aFile
.RE
.PP
Prints a newline separated list of the objects in the sequence to 
.I
aFile
, by sending each individual object a 
.B
printOn:
message\&.  Returns the sequence when there are no more elements left\&.
.PP 
do:
.RS 1
-
.B
do
:
.I
aBlock
.RE
.PP
Performs 
.I
aBlock
for the remaining members of a sequence\&.  
.I
aBlock
should take one argument, which is the element\&.  Typically used as in,
.RS 3

[[aDictionary eachValue] do:{ :each | [each show]; }];
.br

.RE