sequence(3) UNIX System V (Apr 20, 1999) sequence(3)
Sequence
Inherits from:
Object
Class Description
Sequences are used to loop or sequence over a group of
objects. Typically, an Sequence instance is generated by
using some method like OrdCltn 's eachElement . Then,
within a loop, one can send next messages to the sequence
until the end is reached (when the next method returns nil
). Finally, after using the sequence, you have to free the
sequence object.
Warning
Using a sequence can lead to problems if, in sequencing over
a collection, that collection is modified, e.g., as in the
following :
id item;
id aSeq;
aSeq = [aCol eachElement];
while ((item = [aSeq next])) [aCol add:something]; /*
WRONG !!! */
aSeq = [aSeq free];
You may not modify a group of objects while sequencing over
its contents.
Method types
Creation
* copy
* free
Interrogation
* size
Accessing
* next
* peek
* previous
* first
* last
Printing
* printOn:
Performing
* do:
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sequence(3) UNIX System V (Apr 20, 1999) sequence(3)
Methods
copy
- copy
Returns a copy of the sequence. Can be used independently
of the original sequence.
free
- free
Frees the receiver, but not the objects in the collection
being sequenced over.
size
- ( unsigned ) size
Returns the total number of items in the sequence.
next
- next
Returns the next object in the sequence if there is one and
advances the sequence. When it reaches the end of the
sequence, returns nil .
peek
- peek
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 nil .
previous
- previous
Returns the object that was returned by the last next
message. If there were no next messages since the sequence
was created, or the sequence is empty, returns nil .
Doesn't affect the current position in the sequence.
first
- first
Returns the first object in the sequence, unlesss there are
no members in the sequence, in which case it returns nil .
Doesn't affect the current position in the sequence.
last
- last
Returns the last object in the sequence, unlesss there are
no members in the sequence, in which case it returns nil .
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sequence(3) UNIX System V (Apr 20, 1999) sequence(3)
Doesn't affect the current position in the sequence.
printOn:
- printOn :(IOD) aFile
Prints a newline separated list of the objects in the
sequence to aFile , by sending each individual object a
printOn: message. Returns the sequence when there are no
more elements left.
do:
- do : aBlock
Performs aBlock for the remaining members of a sequence.
aBlock should take one argument, which is the element.
Typically used as in,
[[aDictionary eachValue] do:{ :each | [each show]; }];
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