Presentation

LocalTrack interacts exclusively with variables of type Number.

The feature is based on "operating expressions ", which means that the operations to be executed are specified in a character string and are no longer programmed directly in the triggers.

LocalTrack manipulates the values of numbers as binary expressions: the operating expressions can thus be based on 2 logics: the indexes of the bits and the value of the bits.

Binary concepts

This article is not intended to be a course in binary trading, but for those who are not at ease with the vocabulary, here is a short summary of the terms most commonly used to understand Nuggets.

• A binary expression is a sequence of 0s and 1s;
• Each 0 and 1 occupies a space called a bit;
• A bit can therefore be equal to 0 or 1.
• A bit location is characterised by its index.
• Indexes are numbered from 0 and start from the right.
• The decimal value of a bit is calculated by taking 2 to the power of index, i.e. 2 ^index.

The interest

The interest of a binary expression lies in its use as an array storing data:

• the data must answer True/False, Yes/No, etc. to a problem or question;
• they all belong to the same category within a single binary expression.

For example, you can store all the slides in a scene in Storyline in a binary expression:

• its index in the scene will correspond to the index in the binary expression ;
• when visited, the bit in the expression will swap to 1.

With these concepts in mind, let's move on to initialising the functionality in your .STORY file.

Initialisation and parameters

Variables

LocalTrack always works with binomial variables:

• a variable of type Text to state the operations to be performed and
• a variable of type Number to return the result of the operations if there is a result.

For the purposes of this article, we'll call them Tracking and Result.

Trigger

Let's now create the trigger which will execute the processing of the operative expressions passed via the Tracking variable. This trigger will be created on the Main Slide Master.

Storyline trigger

When 'Tracking' changes
- Execute 'JavaScript'
    If 'Tracking' ≠ value '(empty)'

And in the JavaScript Editor :

JavaScript

LocalTrack.parse('Tracking','Result');

Additional informations

LocalTrack.parse accepts a third Text typed argument.

This argument defines the suffix to be assigned to additional variables to be created:

• variables must be of type Text;
• They must be named by combining the suffix and the names of the variables used, either as binomial variables or in operative expressions;
• they systematically return the binary values in the form of a sequence of 0' and1' of the associated variables;
• They are intended to be used with the % processor in text fields.
  Ex : %Tracking_binary%, %Result_binary%, %maVariable_binary%, etc.

The feature is now ready to be used in a project.

Utilisation

Let's look at an example straight away to understand how to use LocalTrack.

Given a variable myVar equal to 0 at the initial point.

Storyline trigger

When the user clicks 'My Button 1'
- Set 'Tracking' to value 'myVar+1' 

The Tracking text variable receives an operating expression, the trigger created in the initialisation phase reacts.

Let's try to break down this operation as LocalTrack processes it. In this example, we "add 1". The result of this operation stores 2 in the myVar variable.

Why?

Let's return to the explanation of number manipulation given earlier in the section "Principle": expressions can be based on the bit indexes or on the bit values.

Here, the + indicates that the operation must be based on the indexes. The operation can be interpreted as follows: add to myVar (which is equal to 0) a bit equal to 1 in index 1, i.e. 2¹. The result is: 0+2=2.

Let's carry out another operation.

Storyline trigger

When the user clicks 'My Button 4'
- Set 'Tracking' to value 'myVar+4' 

The operation can be interpreted as follows: add to myVar (which is equal to 2 now) a bit equal to 1 in index 4, i.e. 2⁴, or 2+16=18. The binary value of myVar is indeed 10010.

The interest

Performing an operation using operand expressions always gives the same result. No matter how many times myVar+1 is run, the result will always return 2.

Adding 1 in decimal format from Storyline triggers increments the variable by 1 each time the trigger is executed.

Of course, addition is not the only operation that can be performed. Let's take a look at the operations interpreted by LocalTrack.

Supported operations

LocalTrack supports several operational expressions, each of which works in a specific way.

Here is the complete list (N being equal to 2ⁿ):

Now let's see how to use them!

Handling operations

Rules on operating expressions

An operating expression is created by combining a variable name, an operand and a value in a character string. This string will be transmitted to the processing variable.

Ex : myVariable+5, myVariable|32, myVariable-5, myVariable~32, etc.

The processing of each operative expression performs each operation on the value of the variable and returns the result in the variable.

Multiple operations

Several operations can be entered in a chain in the same operating expression. Operations are performed from left to right.

Ex : myVariable+2+5+7

The operation is equivalent to performing the sum of all the bits : 2²+2⁵+2⁷ = 4 + 32 + 128 = 164

The sum of the bits is added to the value of myVariable and returned to this variable.

Note that myVariable|164 is equivalent.

Conditional operations

Conditional operations are used to find out the value of one or more bits in a binary expression.

They are performed with the conditional operands ? to return the bit at the index passed to the right of the operand, and & to return the bits identical to the binary expression passed to the right of the operand.

Ex : myVariable?5 returns the bit in index 5 of the variable myVariable

The result of this operation is either 0 if the bit contained 0, or 32 (2⁵) if the bit contained 1.

Conditional operations can also be performed using the sum of several bits.

Ex : myVariable&164 returns the sum of bits n°2, n°5 and n°7 of the variable myVariable.

Operations with variables

Operative expressions can be created using variable names to the right of the operands.

Ex: myVariable+indexButtonX, myVariable&progressChapX, etc.

In this way, declaring a variable at one point in a project and using it in the operative expressions makes development easier and more flexible.

Similarly, it is possible to link several operations with one or more variables in an operative expression.

Storyline triggers

When the timeline starts on 'this slide' 
- Set 'Correct' to value '164' 

When the user clicks 'Button 1'
- Set 'Tracking' to value 'myVariable+1&Correct' 
- // Etc.

When the user clicks 'Button 2'
- Set 'Tracking' to value 'myVariable+2&Correct' 
- // Etc.