Variables

Variables are a way of creating and manipulating a named value, in the same way that algebra uses names to refer to a value. A Variable is useful as a named container to store a value for later use in one or more places in a KookaBlockly script.

Examples of typical Variable names are X, Y and Z when referring to cartesian coordinates; H, W and D as dimensions of an object; and i or j as an index into a List. Variable names can of course be longer, for example height, or temperature

When KookaBlockly is first started, or when a new script is started, the Variables palette looks like this Fig. 66.

Fig. 66 The initial Variables palette

Create Variable

Clicking on “Create variable” brings up a dialogue box, shown in Fig. 67, where the user can define the Variable’s name. Type in a name and then click on OK. The figure shows an example name "my_variable".

Fig. 67 Creating a Variable named my_variable

Once a new Variable has been created, the new Variable will be available in the Variables palette.

It is possible to right-click while hovering over the Variable block in the palette to reveal a number of actions which can be selected by then clicking on them:

1. Delete the variable - removes the Variable, and its associated blocks if it was the only Variable.

2. Rename the variable - brings up a dialogue box, as for creating a Variable, in which the new name can be typed. The new name must contain at least one visible character and not be the same as any other Variable.

3. Help - this option does not yet work. It is intended eventually to display Help text.

Set Variable

Using this block, a value can be assigned to a Variable by attaching a value block to its input. The value can be a number, a boolean, or a character string.

The Variable to be assigned the value can be selected from the drop-down-list.

The drop-down list also has some other choices:

1. Rename variable - brings up a dialogue box in which the new name can be typed. The new name must comprise at least one visible character and must not be a duplicate name.

2. Delete the variable - removes the Variable and its associated blocks from the script.

Change Variable

This action block allows the user to change the selected Variable by a number specified by the input numerical value.

This block will only work for numerical variables and will only accept numerical values.

Character strings and boolean values will not be accepted.

The example in Fig. 68 illustrates how this block may be used as a counter.

Fig. 68 Example script counts button presses

Three variables are set up: count_b, count_c and count_d to count the number of times buttons B, C and D are pressed.

The running totals are printed on the Kookaberry’s display, as shown in Fig. 69.

Fig. 69 The Kookaberry display resulting from Fig. 68

Variable Value

This value block allows a user to attach a variable’s value to the input of another block.

The example in Fig. 70 reads a temperature from a sensor once per 5 seconds, storing it in a Variable named "temperature", then using the stored value to perform a conversion calculation and display the original and converted values on the Kookaberry display:

Fig. 70 Example script reads converts temperature readings to Fahrenheit