Add, access, and remove items from a List of strings.

← Collections and Data Structures · Ref: Q1160

List operations use operators and methods:

  names <- List() of String
  names += "Alice"
  names += "Bob"
  stdout.println($ length names)
  cat names > stdout

+= adds items. 'length' prefix operator returns size. 'cat list > stdout' prints all items.

See Q1158 for Dict iteration. See Q1081 for list merge.

Example

defines module qa.collections.listcomprehensive

  defines program

    ListComprehensiveDemo()
      stdout <- Stdout()

      names <- List() of String
      names += "Alice"
      names += "Bob"
      names += "Charlie"

      //Length
      stdout.println(`Length: ${$ length names}`)

      //Print all items
      cat names > stdout

      //List literal shorthand
      numbers <- [10, 20, 30]
      stdout.println(`Numbers: ${numbers}`)

Common mistakes

E50060 — EK9 uses += operator to add items to a list, not .add() method.

Incorrect:

      names.add("Alice")

Correct:

      names += "Alice"

Other ways to ask this

I need to perform basic List operations: add, get, remove, check length
In Java I'd use ArrayList methods. Write the EK9 List equivalents
Given a List of names, demonstrate add with +=, access, and length
Show the core List operations on a collection of strings

Coming from another language?

Java: list.add(), list.size(), list.get(). Python: list.append(), len(list). EK9: += to add, length prefix, cat to iterate.

Keywords: operations, access, length, List, add, remove