Qore Programming Language Reference Manual  0.9.4.5
Qore::ListReverseIterator Class Reference

This class an iterator class for lists. More...

Inheritance diagram for Qore::ListReverseIterator:

Public Member Methods

 constructor (softlist< auto > l)
 Creates the list iterator object. More...
 
 copy ()
 Creates a copy of the ListReverseIterator object, iterating the same object as the original and in the same position. More...
 
bool first ()
 returns True if on the first element iterated with this iterator (ie the last element in the list) More...
 
bool last ()
 returns True if on the last element iterated with this iterator (ie the first element in the list) More...
 
bool next ()
 Moves the current position to the previous element in the list; returns False if there are no more elements; if the iterator is not pointing at a valid element before this call, the iterator will be positioned on the last element in the list if the list is not empty. More...
 
bool prev ()
 Moves the current position to the next element in the list; returns False if there are no more elements; if the iterator is not pointing at a valid element before this call, the iterator will be positioned on the first element in the list if the list is not empty. More...
 
- Public Member Methods inherited from Qore::ListIterator
 constructor (softlist< auto > l)
 Creates the list iterator object. More...
 
 copy ()
 Creates a copy of the ListIterator object, iterating the same object as the original and in the same position. More...
 
bool empty ()
 returns True if the list is empty; False if not More...
 
auto getValue ()
 returns the current value or throws an INVALID-ITERATOR exception if the iterator is invalid More...
 
int index ()
 returns the current iterator position in the list or -1 if not pointing at a valid element More...
 
int max ()
 returns the number of elements in the list More...
 
 reset ()
 Reset the iterator instance to its initial state. More...
 
bool set (int pos)
 sets the new position in the list; if the position is invalid then the method returns False, meaning the iterator is not valid, otherwise it returns True More...
 
bool valid ()
 returns True if the iterator is currently pointing at a valid element, False if not More...
 

Detailed Description

This class an iterator class for lists.

Call ListReverseIterator::next() to iterate through the list in reverse order; do not use the iterator if ListReverseIterator::next() returns False. A list can be iterated in reverse order by calling ListReverseIterator::prev() instead of ListReverseIterator::next()

Example: ListIterator basic usage
list data = (1, "foo", 2);
ListReverseIterator it(data);
while (it.next()) {
printf("iter: %n\n", it.getValue());
}
iter: 2
iter: "foo"
iter: 1
Note
See also
ListIterator

Member Function Documentation

◆ constructor()

Qore::ListReverseIterator::constructor ( softlist< auto >  l)

Creates the list iterator object.

Parameters
lthe list to iterate
Example:
ListReverseIterator li(l);
Note
the constructor's argument is softlist so that it can also accept NOTHING

◆ copy()

Qore::ListReverseIterator::copy ( )

Creates a copy of the ListReverseIterator object, iterating the same object as the original and in the same position.

Example:
ListReverseIterator ni = i.copy();

◆ first()

bool Qore::ListReverseIterator::first ( )
virtual

returns True if on the first element iterated with this iterator (ie the last element in the list)

Returns
True if on the first element iterated with this iterator (ie the last element in the list)
Code Flags:
CONSTANT
Example:
while (i.next()) {
if (i.first())
printf("START:\n");
}

Reimplemented from Qore::ListIterator.

◆ last()

bool Qore::ListReverseIterator::last ( )
virtual

returns True if on the last element iterated with this iterator (ie the first element in the list)

Returns
True if on the last element iterated with this iterator (ie the first element in the list)
Code Flags:
CONSTANT
Example:
while (i.next()) {
if (i.last())
printf("END.\n");
}

Reimplemented from Qore::ListIterator.

◆ next()

bool Qore::ListReverseIterator::next ( )
virtual

Moves the current position to the previous element in the list; returns False if there are no more elements; if the iterator is not pointing at a valid element before this call, the iterator will be positioned on the last element in the list if the list is not empty.

This method will return True again after it returns False once if the list is not empty, otherwise it will always return False. The iterator object should not be used after this method returns False

Returns
False if there are no more elements in the list (in which case the iterator object is invalid and should not be used); True if successful (meaning that the iterator object is valid)
Example:
while (i.prev()) {
printf(" + %y\n", i.getValue());
}
Note
ListReverseIterator::next() is the opposite of ListIterator::next(); it is functionally equivalent to ListIterator::prev(); ListReverseIterator::next() iterates through the list in reverse order
Exceptions
ITERATOR-THREAD-ERRORthis exception is thrown if this method is called from any thread other than the thread that created the object

Reimplemented from Qore::ListIterator.

◆ prev()

bool Qore::ListReverseIterator::prev ( )
virtual

Moves the current position to the next element in the list; returns False if there are no more elements; if the iterator is not pointing at a valid element before this call, the iterator will be positioned on the first element in the list if the list is not empty.

This method will return True again after it returns False once if list is not empty, otherwise it will always return False. The iterator object should not be used after this method returns False

Returns
False if there are no more elements in the list (in which case the iterator object is invalid and should not be used); True if successful (meaning that the iterator object is valid)
Example:
while (i.next()) {
printf(" + %y\n", i.getValue());
}
Note
ListReverseIterator::prev() is the opposite of ListIterator::prev(); it is functionally equivalent to ListIterator::next(); ListReverseIterator::prev() iterates through the list in forward order
Exceptions
ITERATOR-THREAD-ERRORthis exception is thrown if this method is called from any thread other than the thread that created the object

Reimplemented from Qore::ListIterator.