Variables#

Introduction #

The Variables blocks in VEXcode AIR allow for storing and managing data, including numbers, Boolean values, lists, and 2D lists.

To make a variables blocks appear you must first create a variable. Variables are created using the Make buttons in the Variables category. All variables are global by default, meaning they can be used anywhere in the project.

Below is a list of available blocks:

Numeric Variables - Store and modify numbers.

numeric variable — Reports the value of a numeric variable.
set numeric variable — Assigns a value to a numeric variable.
change numeric variable — Increases or decreases a numeric variable by a set amount.

Boolean Variables — Store True or False values.

Boolean variable — Reports the value of a Boolean variable.
set Boolean variable — Assigns a True or False value to a Boolean variable.

Lists — Store and manage collections of values.

list item — Reports a value from a list based on its position.
replace list item — Updates a specific item in a list.
set list items — Assigns values to a list.
length of list — Returns the number of items in a list.

2D Lists — Store and manage collection of values in a grid.

2D list item — Reports a value from a specific row and column in a 2D list.
replace 2D list item — Updates a specific item in a 2D list.
set 2D list items — Assigns values to a 2D list.
length of 2D list — Returns the number of rows or columns in a 2D list.

numeric variable #

The numeric variable reporter block is used to report the numeric value assigned to the variable.

The Numeric variable reporter block.#

    (my_variable)

Parameter	Description
	This block has no parameters.

Example

  when started :: hat events
  [Use a variable to fly forward and back the same distance.]
  set [fly_distance v] to [90]
  take off to [500] [mm v] ▶
  move [forward v] for (fly_distance) [mm v] ▶
  wait (1) seconds
  move [backward v] for (fly_distance) [mm v] ▶
  wait (1) seconds
  land ▶

set numeric variable #

The set numeric variable block assigns a value to a numeric variable.

Parameter	Description
variable	The numeric variable to assign a value to. Users can select an existing variable, rename it, or delete it.
value	The number assigned to the variable (can be a whole number, decimal, or numeric block).

Example

  when started :: hat events
  [Set a variable to fly forward and back the same distance.]
  set [fly_distance v] to [90]
  take off to [500] [mm v] ▶
  move [forward v] for (fly_distance) [mm v] ▶
  wait (1) seconds
  move [backward v] for (fly_distance) [mm v] ▶
  wait (1) seconds
  land ▶

change numeric variable #

The change numeric variable block increases or decreases a variable’s value by a given amount.

The Change Numeric Variable stack block.#

    change [my_variable v] by (1)

Parameter	Description
variable	The numeric variable to modify. Users can select an existing variable, rename it, or delete it.
value	The amount to increase or decrease the variable by.

Example

  when started :: hat events
  [Fly forward for 50, 150, and 250mm.]
  set [fly_distance v] to [50]
  take off to [500] [mm v] ▶
  repeat (3)
    move [forward v] for (fly_distance) [mm v] ▶
    wait (1) seconds
    change [fly_distance v] by (100)
  end
  land ▶

Boolean variable #

The Boolean variable block is used to report either a True or False value.

The Boolean Variable reporter block.#

    <my_boolean>

Parameter	Description
	This block has no parameters.

Example

  when started :: hat events
  [Display a message if the variable is set to True.]
  set [my_boolean v] to <true v>
  if <my_boolean> then
    print [Boolean is True!] on screen ▶
  end

set Boolean variable #

The set Boolean variable block assigns a True or False value to a Boolean variable.

The Set Boolean Variable stack block.#

    set [my_boolean v] to <true v>

Parameter	Description
variable	The Boolean variable to assign a value to. Users can select an existing variable, rename it, or delete it.
value	A Boolean value (True or False).

Example

  when started
  [Display different messages based on the Boolean value.]
  set [my_boolean v] to <true v>
  if <my_boolean> then
    print [It's true!] on screen ▶
  else
    print [That's false...] on screen ▶
  end

list item #

The list item block is used to report the value of an item in a list.

The List Item reporter block.#

    (item (1) of [my_list v])

Parameter	Description
index	The position of the item in the list (starting at 1).
variable	The list variable to report an item from. Users can select an existing list, rename it, or delete it.

Example

  when started
  [Display the second item from a list.]
  set [my_list v] to [Drone] [Controller] [Headset]
  print (item (2) of [my_list v]) on screen ▶

replace list item #

The replace list item block updates a specific item in a list.

The Replace List Item stack block.#

    replace item (1) of [my_list v] to (1)

Parameter	Description
variable	The list variable containing the item to modify. Users can select an existing list, rename it, or delete it.
index	The position of the item in the list (starting at 1).
value	The new value assigned to the specified list item.

Example

  when started
  [Replace the first item in a list with "AprilTag".]
  set [my_list v] to [Drone] [Controller] [Headset]
  replace item (1) of [my_list v] to [AprilTag]
  print (item (1) of [my_list v]) on screen ▶

set list items #

The set list items block sets every item in the list to the entered values.

The Set List Items stack block.#

    set [my_list v] to [0] [0] [0]

Parameter	Description
variable	The list variable being assigned values. Users can select an existing list, rename it, or delete it.
values	The values to store in the list, entered as individual items.

Example

  when started
  [Display the last item in a list.]
  set [my_list v] to [Red] [Green] [Blue]
  print (item (3) of [my_list v]) on screen ▶

length of list #

The length of list block reports the number of items in a list.

The Length of List reporter block.#

    (length of [my_list v])

Parameter	Description
variable	The list variable to report the length of. Users can select an existing list, rename it, or delete it.

Example

  when started
  [Display how many items are in a list.]
  set [my_list v] to [Red] [Green] [Blue]
  print (length of [my_list v]) on screen ▶

2D list item #

The 2D list item block is used to report the value of an item in a 2D list.

The 2D List Item reporter block.#

    (item (1) (1) of [my_2d_list v])

Parameter	Description
row	The row of the item (starting at 1).
column	The column of the item (starting at 1).
variable	The 2D list variable to report an item from. Users can select an existing 2D list, rename it, or delete it.

Example

  when started
  [Display an item from a 2D list.]
  set [my_2d_list v] to ([1][Drone]) ([4][Propeller]) 
  print (item (2) (2) of [my_2d_list v]) on screen ▶

replace 2D list item #

The replace 2D list item block updates a specific item in a 2D list.

The Replace 2D List Item stack block.#

    replace item (1) (1) of [my_2d_list v] to (1)

Parameter	Description
row	The row index of the item (starting at 1).
column	The column index of the item (starting at 1).
variable	The 2D list variable containing the item to modify. Users can select an existing 2D list, rename it, or delete it from the drop-down menu.
value	The new value assigned to the specified 2D list item.

Example

  when started
  [Replace a value in a 2D list and print the updated item.]
  set [my_2d_list v] to ([1][Drone]) ([4][Propeller]) 
  replace item [2] [2] of [my_2d_list v] to [Headset]
  print (item (2) (2) of [my_2d_list v]) on screen ▶

set 2D list items #

The set 2D list items block sets every item in the 2D list to the entered values.

The Replace 2D List Item stack block.#

    set [my_2d_list v] to ([0][0]) ([0][0])

Parameter	Description
variable	The 2D list variable being assigned values. Users can select an existing 2D list, rename it, or delete it.
values	The values to store in the 2D list, entered row by row.

Example

  when started
  [Display an item from a 2D list.]
  set [my_2d_list v] to ([1][Drone]) ([4][Propeller]) 
  print (item (1) (2) of [my_2d_list v]) on screen ▶

length of 2D list #

The length of 2D list block reports the number of rows or columns in a 2D list.

The Length of 2D List reporter block.#

    length of [my_2d_list v] [rows v]

Parameter	Description
variable	The 2D list variable to check the length of. Users can select an existing 2D list, rename it, or delete it.
rows/columns	Whether to report the number of rows or column.

Example

  when started
  [Set a 2D list and print the number of rows it has.]
  set [my_2d_list v] to ([1][Drone]) ([4][Propeller]) 
  print (length of [my_2d_list v] [rows v]) on screen ▶