Page 254 - Learn To Program With Scratch

Even number
 of items.

Find the average of
 the two middle
numbers.

Odd number
 of items.

 The median is the
middle number.

Figure 9-25: Finding the median value of a sorted list of numbers

The procedure uses an if/else block to handle the two cases of even and
odd lists. If the number of items in the list divides by 2 with no remainder
(that is, the list has an even number of items) u, the median variable is cal-
culated as the average of the middle two numbers v. Otherwise, the list has
an odd number of items w, and the median variable is set equal to the num-
ber in the middle of the list x.
We’ve covered a lot of ground so far, so it’s time to apply our newfound
knowledge to something more challenging. The rest of this chapter walks
through several examples that demonstrate how to use lists in more com-
plex applications.

Scratch Projects

In this section, you’ll explore practical Scratch projects that highlight dif-
ferent aspects of lists. I’ll also introduce some new ideas and techniques
that you can use in your own creations.

The Poet

Poet .sb2 Let’s kick off this chapter’s projects with a poem generator. Our artificial
poet selects words randomly from five lists (article, adjective, noun, verb, and
preposition) and combines them according to a fixed pattern. To give our
poems a central theme, all the words in these lists are somehow related to
love and nature. (Of course, we might still end up with some silly poetry,
but that’s just as fun!)

232 Chapter 9
www.it-ebooks.info