Iterators is an actively used design pattern created in 1974. In computer programming, an iterator is an object that enables a programmer to traverse a container, particularly lists.[1][2][3] Various types of iterators are often provided via a container's interface.

45Years Old

Languages with Iterators include cpp, java, matlab, python, ruby, rust

Example from cpp:

std::vector<int> items;
items.push_back(5);  // Append integer value '5' to vector 'items'.
items.push_back(2);  // Append integer value '2' to vector 'items'.
items.push_back(9);  // Append integer value '9' to vector 'items'.

for (auto it = items.begin(); it != items.end(); ++it) {  // Iterate through 'items'.
  std::cout << *it;  // And print value of 'items' for current index.
}

Example from java:

Iterator iter = list.iterator();
//Iterator<MyType> iter = list.iterator();    in J2SE 5.0
while (iter.hasNext()) {
    System.out.print(iter.next());
    if (iter.hasNext())
        System.out.print(", ");
}

Example from matlab:

% Define an array of integers
myArray = [1,3,5,7,11,13];

for n = myArray
   % ... do something with n
   disp(n)  % Echo integer to Command Window
end

Example from python:

https://www.w3schools.com/python/python_iterators.asp

Example from ruby:

(0...42).each do |n|
  puts n
end

Example from rust:

for n in 0..42 {
  println!("{}", n);
}

Last updated August 9th, 2020

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