41. An other way to repeat

Here we present a different way to repeat a given instruction, one that is more specific to the instruction that we want to repeat. Suppose we want to turn right or turn around but want to have a single function name to remember. One way to do it is as follows:

function turn(nb){
    for (var i = 0; i < nb; i++) {
        turn_left();
    }
}

Using this definition, turn_right() would be written as turn(3) and turn_around() would be written as turn(2). Try it!

41.1. Having a default behaviour

Remember how take() and take("token") are equivalent? Would it be nice to have something similar for turn() where turn(), with no argument, would be equivalent to a single turn_left() instruction?

This can be accomplished as follows:

function turn(nb){
    nb = nb || 1;
    for (var i = 0; i < nb; i++) {
        turn_left();
    }
}

In the code above, we make use of the logical OR operator, ||, which we will see in more details later. Consider this as a simple example to whet your appetite. A quick explanation is as follows:

• a || b is equal to b if a is false or undefined.
• If the function argument is not specified, it is undefined; when this happens, nb take the value 1.
• Note that, if a number less than 1 or a string is passed as an argument, the for loop is skipped and Reeborg does not turn.

Try it!

Write programs that make use of the code samples above.