Qore Programming Language Reference Manual  0.8.13.6
Qore::ListIterator Class Reference

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

Inheritance diagram for Qore::ListIterator:

Public Member Functions

 constructor (softlist 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...
 
bool first ()
 returns True if on the first element of the list 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...
 
bool last ()
 returns True if on the last element of the list More...
 
int max ()
 returns the number of elements in the list More...
 
bool next ()
 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...
 
bool prev ()
 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...
 
 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 ListIterator::next() to iterate through the list; do not use the iterator if ListIterator::next() returns False. A list can be iterated in reverse order by calling ListIterator::prev() instead of ListIterator::next()

Example: ListIterator basic usage
list data = (1, "foo", 2);
ListIterator it(data);
while (it.next()) {
printf("iter: %n\n", it.getValue());
}
iter: 1
iter: "foo"
iter: 2
Note
  • In general, the ListIterator class is not designed to be accessed from multiple threads; it was created without locking for fast and efficient use when used from a single thread. For methods that would be unsafe to use in another thread, any use of such methods in threads other than the thread where the constructor was called will cause an ITERATOR-THREAD-ERROR to be thrown.
See also
ListReverseIterator

Member Function Documentation

◆ constructor()

Qore::ListIterator::constructor ( softlist  l)

Creates the list iterator object.

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

◆ copy()

Qore::ListIterator::copy ( )

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

Example:
ListIterator ni = i.copy();

◆ empty()

bool Qore::ListIterator::empty ( )
virtual

returns True if the list is empty; False if not

Returns
True if the list is empty; False if not
Code Flags:
CONSTANT
Example:
if (i.empty())
printf("the list is empty\n");

Implements Qore::AbstractQuantifiedIterator.

◆ first()

bool Qore::ListIterator::first ( )
virtual

returns True if on the first element of the list

Returns
True if on the first element of the list
Code Flags:
CONSTANT
Example:
while (i.next()) {
if (i.first())
printf("START:\n");
}

Implements Qore::AbstractQuantifiedIterator.

Reimplemented in Qore::ListReverseIterator.

◆ getValue()

auto Qore::ListIterator::getValue ( )
virtual

returns the current value or throws an INVALID-ITERATOR exception if the iterator is invalid

Returns
the current value or throws an INVALID-ITERATOR exception if the iterator is invalid
Code Flags:
RET_VALUE_ONLY
Example:
while (i.next()) {
printf("+ %y\n", i.getValue());
}
Exceptions
INVALID-ITERATORthe iterator is not pointing at a valid element
ITERATOR-THREAD-ERRORthis exception is thrown if this method is called from any thread other than the thread that created the object

Implements Qore::AbstractIterator.

◆ index()

int Qore::ListIterator::index ( )

returns the current iterator position in the list or -1 if not pointing at a valid element

Returns
the current iterator position in the list or -1 if not pointing at a valid element
Code Flags:
CONSTANT
Example:
while (i.next()) {
printf("+ %d/%d: %y\n", i.index(), i.max(), i.getValue());
}

◆ last()

bool Qore::ListIterator::last ( )
virtual

returns True if on the last element of the list

Returns
True if on the last element of the list
Code Flags:
CONSTANT
Example:
while (i.next()) {
if (i.last())
printf("END.\n");
}

Implements Qore::AbstractQuantifiedIterator.

Reimplemented in Qore::ListReverseIterator.

◆ max()

int Qore::ListIterator::max ( )

returns the number of elements in the list

Returns
the number of elements in the list
Code Flags:
CONSTANT
Example:
while (i.next()) {
printf("+ %d/%d: %y\n", i.index(), i.max(), i.getValue());
}

◆ next()

bool Qore::ListIterator::next ( )
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());
}
Exceptions
ITERATOR-THREAD-ERRORthis exception is thrown if this method is called from any thread other than the thread that created the object

Implements Qore::AbstractIterator.

Reimplemented in Qore::ListReverseIterator.

◆ prev()

bool Qore::ListIterator::prev ( )
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());
}
Exceptions
ITERATOR-THREAD-ERRORthis exception is thrown if this method is called from any thread other than the thread that created the object

Implements Qore::AbstractBidirectionalIterator.

Reimplemented in Qore::ListReverseIterator.

◆ reset()

Qore::ListIterator::reset ( )

Reset the iterator instance to its initial state.

Reset the iterator instance to its initial state

Example
i.reset();
Exceptions
ITERATOR-THREAD-ERRORthis exception is thrown if this method is called from any thread other than the thread that created the object

◆ set()

bool Qore::ListIterator::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

Parameters
posthe new position for the iterator with 0 as the first element
Returns
False, meaning the iterator is not valid, otherwise it returns True
Example:
if (!i.set(pos))
throw "INVALID-POSITION", sprintf("%d is an invalid position", pos);
Exceptions
ITERATOR-THREAD-ERRORthis exception is thrown if this method is called from any thread other than the thread that created the object

◆ valid()

bool Qore::ListIterator::valid ( )
virtual

returns True if the iterator is currently pointing at a valid element, False if not

Returns
True if the iterator is currently pointing at a valid element, False if not
Code Flags:
CONSTANT
Example:
if (i.valid())
printf("current value: %y\n", i.getValue());

Implements Qore::AbstractIterator.