Iterators: Difference between revisions
Created Nim solution.
(Created Nim solution.) |
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Saturday, Wednesday, Tuesday
Purple, Yellow, Orange
</pre>
=={{header|Nim}}==
Nim defines iterators for collection types such as arrays, sequences, sets, tables, etc. But it allows also to define our own iterators. There exists two kinds of such iterators: inline iterators (the current default) and closure iterators. Inline iterators are expanded, closure iterators are not.
In our solution, we use standard iterators and our own iterators.
<syntaxhighlight lang="Nim">import std/lists
# Days stored in an array.
let days = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"]
# Colors stored in a doubly linked list.
let colors = ["Red", "Orange", "Yellow", "Green", "Blue", "Purple"].toDoublyLinkedList
### To print the elements of "days", we use a standard iterator.
echo "Content of “days” array:"
for day in days:
echo day
echo()
### To print the elements of "colors", we use a standard iterator.
echo "Content of “colors” list:"
for color in colors:
echo color
echo()
### To print the first, fourth an fifth elements
### of "days", we use a standard iterator.
echo "First, fourth and fifth elements of “days”:"
for i, day in days:
if i + 1 in [1, 4, 5]:
echo day
echo()
### To print the first, fourth an fifth elements
### of "colors", we must define our own iterator.
iterator enumerate[T](list: DoublyLinkedList[T]): (int, T) =
## Yield the successive (index, value).*
## First index is 0.
var i = 0
var node = list.head
while node != nil:
yield (i, node.value)
node = node.next
inc i
echo "First, fourth and fifth elements of “colors”:"
for i, color in colors.enumerate:
if i + 1 in [1, 4, 5]:
echo color
echo()
### To print the last, fourth to last, and fifth to last
### elements of "days", we must define our own iterator.
iterator revItems[T](a: openArray[T]): (int, T) =
## Starting from end of array, yield (index, value).
## First index is 1.
for i in countdown(a.high, 0):
yield (a.len - i, a[i])
echo "Last, fourth to last and fifth to last elements of “days”:"
for i, day in days.revItems:
if i in [1, 4, 5]:
echo day
echo()
### To print the last, fourth to last, and fifth to last
### elements of "colors", we must define our own iterator.
iterator revItems[T](list: DoublyLinkedList[T]): (int, T) =
## Starting from end of the list, yield (index, value).
## First index is 1.
var i = 1
var node = list.tail
while node != nil:
yield (i, node.value)
node = node.prev
inc i
echo "Last, fourth to last and fifth to last elements of “colors”:"
for i, color in colors.revItems:
if i in [1, 4, 5]:
echo color
</syntaxhighlight>
{{out}}
<pre>Content of “days” array:
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Content of “colors” list:
Red
Orange
Yellow
Green
Blue
Purple
First, fourth and fifth elements of “days”:
Sunday
Wednesday
Thursday
First, fourth and fifth elements of “colors”:
Red
Green
Blue
Last, fourth to last and fifth to last elements of “days”:
Saturday
Wednesday
Tuesday
Last, fourth to last and fifth to last elements of “colors”:
Purple
Yellow
Orange
</pre>
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