Control

Introduction

The Control blocks in VEXcode IQ (2nd gen) 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 Brain Check button is pressed, then stops all movement.

    when started
    [Move forward until a button is pressed, then stop.]
    drive [forward v]
    wait until <Brain [Check 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, plays a siren until the Brain Check button is pressed, then plays the power down sound.

    when started
    [Play a sound until a button is pressed.]
    repeat until <Brain [Check v] button pressed?>
        play sound [siren v]
        wait (0.5) seconds
    end
    wait (0.5) seconds
    play sound [power down v]

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

When started, plays an alarm while the drivetrain is moving.

    when started
    [Play an alarm while the robot is moving.]
    drive [forward v] for [300] [mm v] ◀ and don't wait
    while <drive is moving?>
        play sound [alarm v]
        wait (0.3) seconds
    end

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 Brain Check button is pressed. If pressed, the robot turns right.

    when started
    [Turn in a circle if a button is pressed.]
    forever
    if <Brain [Check v] button 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

When started, repeatedly turns right when the Brain Check button is pressed; otherwise, it plays a siren.

    when started
    [Repeatedly play a sound if a button is not pressed.]
    forever
    if <Brain [Check v] button pressed?> then
        turn [right v] for (360) degrees ▶
    else
        play sound [siren v]
        wait (0.5) seconds
    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

When started, turns right if the Brain Right button is pressed, turns left if the Brain Left button is pressed, and stops otherwise.

    when started
    [Turn right if the right button on the brain is pressed, left if the left is pressed, and stop if anything else is pressed.]
    forever
        if <Brain [Right v] button pressed?> then
            turn [right v] for (90) degrees ▶
        else if <Brain [Left v] button pressed?> then
            turn [left v] for (90) degrees ▶
        else
            stop driving
        end
    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 until the Brain Check button is pressed, then stops driving and plays the power down sound.

    when started
    [Stop turning after a button is pressed.]
    forever
    turn [right v]
    if <Brain [Check v] button pressed?> then
    break
    end
    end
    stop driving
    play sound [power down v]

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 until the Brain Check button is pressed, then stops the project.

    when started
    [Stop the project entirely after a button is pressed.]
    forever
    turn [right v]
    if <Brain [Check v] button pressed?> then
    stop project
    end
    end
    play sound [power down v]