Lesson 6.2: Using for Loops to Repeat Robot Actions Cleanly

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Technical Context

Repetitive mechanical tasks: such as pulsing an intake or cycling a scoring mechanism: are prone to "logic bloat" if written line-by-line. Using a for loop ensures code efficiency and allows the programmer to adjust the number of iterations (e.g., 3 gear-clearing pulses) in a single parameter change rather than rewriting blocks of code.

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When a for Loop Is Better Than Repeating Code

The for loop follows the syntax for(initialization; condition; update). It instantiates a local int counter that increments after each pass. In FTC robotics, this is frequently used to cycle mechanisms for a fixed number of iterations rather than relying on inconsistent time-based logic.

The three parts of the for header do distinct jobs:

• Initialization: runs once before the loop starts, creating the counter (e.g., int i = 0)
• Condition: checked before every iteration; the loop stops when this is false (e.g., i < 5)
• Update: runs at the end of every iteration, advancing the counter (e.g., i++)

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Annotated Code

package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
import com.qualcomm.robotcore.eventloop.opmode.Autonomous;
import com.qualcomm.robotcore.hardware.DcMotor;

@Autonomous(name="Pulse_Demo")
public class PulseDemo extends LinearOpMode {

    @Override
    public void runOpMode() {
        DcMotor scoringMotor = hardwareMap.get(DcMotor.class, "scoring");

        waitForStart();

        // Example: Pulsing a scoring motor 5 times
        for (int i = 0; i < 5; i++) {
            scoringMotor.setPower(1.0);
            sleep(100); // 100ms on-pulse
            scoringMotor.setPower(0.0);
            sleep(100); // 100ms pause between pulses

            telemetry.addData("Pulse", i + 1);
            telemetry.update();
        }
    }
}

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Fill-in-the-Blank Practice

1. In the for loop header, the __________ section is executed exactly once before the loop begins.
2. To repeat a block of code exactly 10 times starting at i = 0, the condition should be written as i < __________.
3. The __________ statement is executed at the end of every iteration, typically used to increase the counter.

Show answers

1. initialization (e.g., int i = 0)
2. 10
3. update (e.g., i++)

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Simulator Challenge

Use the simulator below to practice writing a for loop that repeats a fixed robot action exactly three times.

1.Complete the codeWork in fullscreen when you need more room for the editor and visualizer. Where file tabs are available, hover over the tab strip and choose + to create a file or reuse saved code.

2.Run the lifecyclePress Init, then Start. Use the available gamepad or scene controls.

3.Debug the behaviorCheck telemetry, motion, requirements, and hints before opening the answer.

Telemark Unit 6 Simulator

Supports OpMode and LinearOpMode practice with lesson-specific starter code.

Includes loop stepping, runtime tracking, lifecycle controls, and live gamepad input.

Best for practicing loop structure, timers, and safe control flow patterns.

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