Lists

List.

A list is a data type that holds variables of all type be it character, string, function, number etc. The members of this data type are enclosed in []. They have the same functions / features as Arrays have in JavaScript. Example of a List:

myList = ["bread", "jam", "egg"]

display myList # bread, jam and egg.

Declaring List.

As earlier discussed in [Low and High ordered variables](Low and High ordered variables.md), we can declare List in two ways but in this chapter, we'll be discussing Lists declared from parent class. We'll also discuss the methods attached to them.

Before we dive deep, let's list the basics methods attached to the List data type:

• .push()
• .pop()
• .reverse()
• .indexOf()
• .slice()
• .keys()
• .length()

# Remember to call the List module.
call "simple/core/List.sim"

myList = new List(["bread", "jam", "bacon", "eggs"])

The above is our declared List which we'll be using to showcase the methods attached to the List data type.

Adding a new value to the List using .push().

To add a new value to the list, we use the method .push(x), where x is either a boolean, number, function, array or string. Let's test this:

call "simple/core/List.sim"

myList =new List( ["bread", "jam", "bacon", "eggs"])

# To add butter to the list, we do that using the .push() method.

myList.push("butter")

display myList.keys() # bread, jam, bacon, eggs, butter.

Removing a value from the list using the .pop() method.

To remove the value from an array, we must know the indexNumber of the value to be removed.

Note that index numbers of lists start from 0.

Assuming, we want to remove bacon from our list, we execute that by passing the indexNumber as an argument in the .pop() method.

call "simple/core/List.sim"

myList = new List(["bread", "jam", "bacon", "eggs", "butter"])

# Removing bacon where the index number is 2.

myList.pop(2)

display myList.keys() # bread, jam, eggs, butter.

Reversing the List using the .reverse() method.

When we say reversing a list, we actually move the elements from ascending to descending order and vice versa. Let's reverse our List:

call "simple/core/List.sim"

myList =new List( ["bread", "jam", "eggs", "butter"])

# reversing the list.

myList.reverse()

display myList.keys() # butter, eggs, jam, bread.

Getting the value of a Listthrough the use of indexOf().

To get the specific value of a List item using it's index number, we pass the index number into a method .indexOf and it returns the value holding that indexNumber. Let's get the value whose index number is 3 in our List.

call "simple/core/List.sim"

myList = new List(["bread", "jam", "eggs", "butter"])

display myList.indexOf(3)  # displays "butter".

Slicing through a List by using the .slice() method.

This method takes two arguments whereas the list is sliced through the arguments passed in it.

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Getting the members of the List using .keys() method.

To return or get a list of all members of the list, we use the .keys() method. To get all members of our list, myList, we do this:

call "simple/core/List.sim"

myList = new List(["bread", "beans", "rice", "spaghetti"])

display myList.keys() # returns bread, beans, rice, spaghetti.

Retrieving the length of the List using .length().

To get the length of the list, we use the .length() method. Example:

call "simple/core/List.sim"

myList = ["a", "b","c","d","e"]

display test.length() # 4