core :: Iterator :: defaultinit
# Iterators generate a series of elements, one at a time.
#
# They are mainly used with collections and obtained from `Collection::iterator`.
interface Iterator[E]
# The current item.
# Require `is_ok`.
fun item: E is abstract
# Jump to the next item.
# Require `is_ok`.
fun next is abstract
# Jump to the next item `step` times.
#
# ~~~
# var i = [11, 22, 33, 44].iterator
# assert i.item == 11
# i.next_by 2
# assert i.item == 33
# ~~~
#
# `next_by` should be used instead of looping on `next` because is takes care
# of stopping if the end of iteration is reached prematurely whereas a loop of
# `next` will abort because of the precondition on `is_ok`.
#
# ~~~
# i.next_by 100
# assert not i.is_ok
# ~~~
#
# If `step` is negative, this method aborts.
# But specific subclasses can change this and do something more meaningful instead.
#
# Require `is_ok`
fun next_by(step: Int)
do
assert step >= 0
while is_ok and step > 0 do
next
step -= 1
end
end
# Is there a current item ?
fun is_ok: Bool is abstract
# Iterate over `self`
fun iterator: Iterator[E] do return self
# Pre-iteration hook.
#
# Used to inform `self` that the iteration is starting.
# Specific iterators can use this to prepare some resources.
#
# Is automatically invoked at the beginning of `for` structures.
#
# Do nothing by default.
fun start do end
# Post-iteration hook.
#
# Used to inform `self` that the iteration is over.
# Specific iterators can use this to free some resources.
#
# Is automatically invoked at the end of `for` structures.
#
# Do nothing by default.
fun finish do end
# A decorator around `self` that advance self a given number of steps instead of one.
#
# ~~~
# var i = [11, 22, 33, 44, 55].iterator
# var i2 = i.to_step(2)
#
# assert i2.item == 11
# i2.next
# assert i2.item == 33
#
# assert i.item == 33
# ~~~
fun to_step(step: Int): Iterator[E] do return new StepIterator[E](self, step)
end
lib/core/collection/abstract_collection.nit:203,1--285,3