Page 247 - Learn To Program With Scratch

Finding the minimum value in a list follows a similar algorithm. We
start by assuming that the first element in the list is the smallest element
and then use a loop to check the remaining elements. Each time we find
a smaller value, we update the variable that holds the minimum value.

try it out 9-4
Use what you learned in this section to create a procedure called FindMin that
finds the minimum value of the score list .

Finding the Average

FindAverage .sb2 In our next example, we’ll write a procedure that computes the average
score of the numbers stored in our score list. You can find the average of
a sequence of N numbers by first finding their sum and then dividing the
total by N. The procedure shown in Figure 9-18 does exactly that.

This variable is used to hold the
total sum.
Note: You can also use the change sum by block.

Loop through the scores stored in
the list and calculate their sum.

Divide the sum by the number of
scores in the list.

Figure 9-18: Finding the average value of a list of numbers

The FindAverage procedure uses a loop to step through the scores
stored in the list, add them together, and store the result in a variable
named sum. (This variable is initialized to 0 before the start of the loop.)
When the loop terminates, the script calculates the average by dividing
sum by the number of scores, and it saves the result in a variable named
average.
n o t e Pay special attention to the way we accumulated the sum variable inside the
loop. This pattern, known as the accumulator pattern, comes up very often
in programming.

In the next section, we’ll explore how to search and sort lists, two com-
mon problems in programming. I’ll also walk you through some simple
algorithms for performing each operation.

Lists 225

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