Control#

Introduction #

The Control blocks in VEXcode EXP manage the flow of a project by handling loops, conditions, and delaying blocks from running.

A loop is when a computer repeats the same step or group of steps over and over until it is told to stop. A condition is a rule the computer checks to decide what to do next. For example, a robot can move forward if a sensor detects an object.

Below is a list of available blocks:

wait – Pauses blocks from running for a specific duration.
wait until – Pauses blocks from running until a specified condition is met.
repeat – Repeats a set of blocks a specific number of times.
forever – Repeats a set of blocks indefinitely.
repeat until – Repeats a set of blocks until a condition is met.
while – Repeats a set of blocks while a condition remains true.
if – Runs a set of blocks if a condition is true.
if / else – Runs one set of blocks if a condition is true, otherwise runs another.
if / else if / else – Runs different sets of blocks depending on multiple conditions.
break – Exits a repeat, forever, repeat until, or while loop immediately.
stop project – Ends the project.

wait #

The wait stack block pauses blocks from running for a specific amount of time before moving to the next block.

wait stack block#

    wait (1) seconds

Parameters	Description
time	The amount of time to wait, as a positive whole number or decimal in seconds.

Example

When started, moves forward for one second, then stops all movement.#

    when started
    [Move forward for one second, then stop.]
    drive [forward v]
    wait (1) seconds
    stop driving

wait Until #

The wait until stack block pauses blocks from running until a specified condition is met before moving to the next block.

wait until stack block#

    wait until <>

Parameters	Description
condition	The condition that must be met before moving on to the next block.

Example

When started, moves forward until the ◀ button is pressed, then stops all movement.#

    when started
    [Move forward until the ◀ button is pressed, then stop.]
    drive [forward v]
    wait until <Brain [◀ v] button pressed?>
    stop driving

repeat #

The repeat C block runs the blocks inside it a set number of times.

repeat c block#

    repeat [10]
    end

Parameters	Description
times	A whole number that sets how many times the repeat block runs.

Example

    when started
    [Move in a square path.]
    repeat [4]
        drive [forward v] for [150] [mm v] ▶
        turn [right v] for [90] degrees ▶
    end

forever #

The forever C block keeps running the blocks inside it again and again without stopping.

forever c block#

    forever
    end

Parameters	Description
	This block has no parameters.

Example

When started, continuously moves in a square path by moving forward 50 mm and turning right 90 degrees in an infinite loop.#

    when started
    [Move in a square path forever.]
    forever
        drive [forward v] for [150] [mm v] ▶
        turn [right v] for [90] degrees ▶
    end

repeat until #

The repeat until C block runs the blocks inside it repeatedly while the specified condition is not met.

repeat until block#

    repeat until <>
    end

Parameters	Description
condition	An expression or variable that is checked before each loop. If it is False, the blocks continue repeating. If it is True, the loop will stop.

Example

When started, keeps all LEDs red until the screen is pressed, then turns them off.#

    when started
    [Turn until the screen is pressed.]
    repeat until <screen pressed?>
        turn [right v]
    end
    stop driving

while #

The while C block runs the blocks inside repeatedly while the specified condition is met.

while c block#

    while <>
    end

Parameters	Description
condition	An expression or variable that is checked before each loop. If it is True, the blocks continue repeating. If it is False, the loop will stop.

Example

A stack of blocks that begins with a when started block, followed by a comment block reading Display the time after 2 seconds have passed. A wait until block pauses execution until the timer reaches or exceeds two seconds. Once this condition is met, a print block displays the timer value on the screen.#

  when started
  [Display the time for one minute.]
  while <(timer in seconds) [math_less_than v] [60] >
  clear screen
  set cursor to row [1] column [1] on screen
  print (timer in seconds) on screen ▶

if #

The if C block runs the blocks inside if the condition is True.

if block#

    if <> then
    end

Parameters	Description
condition	An expression or variable that is checked when the statement runs. If it is True, the blocks inside the if block will run. If it is False, the blocks are skipped over.

Example

When started, continuously checks if the screen is pressed. If pressed, the robot kicks an object with medium force.#

    when started
    [Turn in a circle if the screen is pressed.]
    forever
    if <screen pressed?> then
    turn [right v] for [360] degrees ▶
    end
    stop driving
    end

if / else #

The if / else C block determines which set of blocks runs based on whether the condition is True or False.

if then else block#

    if <> then
    else
    end

Parameters	Description
condition	An expression or variable that is checked when the statement runs. If it is True, the blocks inside the if block will run. If it is False, it will runs the blocks inside the else block.

Example

if then else block#

    when started
    [Display a message if the screen is being pressed.]
    forever
    clear screen
    set cursor to row [1] column [1] on screen
    if <screen pressed?> then
        print [Pressed!] on screen ▶
    else
        print [Not pressed!] on screen ▶
    end

if / else if / else #

The if / else if / else expandable C block selects which set of blocks runs based on conditions:

if runs its block of code if the condition evaluates as True.
else if checks additional conditions only if all previous conditions evaluated as False. Multiple else if statements can be used.
else runs its block of code only if none of the previous conditions evaluated as True.

if else if else block#

    if <> then
    else if <> then
    else 
    end

Parameters	Description
condition	An expression or variable that is checked when the statement runs. The first condition that is True runs that set of blocks. If all conditions evaluate as False, the blocks inside the else block will run.

Example

if then else block#

    when started
    [Move the robot based on the Controller button is being pressed.]
    forever
    if <[Controller1 v] [▶ v] pressed?> then
        turn [right v]
    else if <[Controller1 v] [◀ v] pressed?> then
        turn [left v]
    else
        stop driving
    end

break #

The break stack block exits a loop immediately. This block can be used inside repeat, repeat until, while, and forever blocks. Break is useful when a loop needs to stop early based on something that happens during the project, like a button being pressed or a sensor detecting an object.

break stack block#

    break

Parameters	Description
	This block has no parameters.

Example

When started, turns right until the screen is pressed, then stops.#

    when started
    [Stop turning after the screen is pressed.]
    forever
    turn [right v]
    if <screen pressed?> then
    break
    end
    end
    stop driving

stop project #

The stop project stack block ends a running project.

stop project block#

    stop project

Parameters	Description
	This block has no parameters.

Example

When started, turns right until the screen is pressed, then stops the project.#

    when started
    [Stop the project entirely after the screen is pressed.]
    forever
    turn [right v]
    if <screen pressed?> then
    stop project
    end
    end