Code Solutions

 /* This program has Karel double a stack of balls that are one spot

 * ahead, and return to the starting position. */
function main() {
    move();
    doubleBalls();
    turnAround();
    move();
    turnAround();
}

/* This doubles a stack of balls. */
function doubleBalls() {
    while (ballsPresent()) {
        takeOnePutTwoBeside();
    }
    move();

    turnAround();
    while (ballsPresent()) {
        moveOneBallBack();
    }

    move();
    turnAround();
}

/* This takes one ball from a pile and puts one more ball
 * in the pile next to it. */
function moveOneBallBack() {
    takeBall();
    move();
    putBall();
    turnAround();
    move();
    turnAround();
}

/* This takes one ball from the pile and places two balls
 * in the pile next to it. */
function takeOnePutTwoBeside() {
    takeBall();
    move();
    putBall();
    putBall();
    turnAround();
    move();
    turnAround();
}

main();