33.0.1. Exercise: Examine the block expressions

| sum |
sum := 0.
#(21 23 53 66 87) do: [:item | sum := sum + item].
sum

• What is the final result of sum?

• Rewrite this piece of code to use explicit array indexing (with the message at: ) to access the array elements. Test your version.

• Rewrite this code using inject:into: (Look at the implementation of inject:into: and its users in the system to understand how to use it).

33.0.2. Exercise: Comparing expressions

You can express in different way the same computation. Have a look at each of them and check the messages that you do not know. Look for their implementation.

| array |
array := #(2 4 4 4 5 5 7 9).
((array - array average) squared sum / (array size - 1)) sqrt 

[ :input | ((input - input average) squared sum / (input size - 1)) sqrt ] 
    value: #(2 4 4 4 5 5 7 9) 

#(2 4 4 4 5 5 7 9) in: [ :input |
    ((input - input average) squared sum / (input size - 1)) sqrt ]

#(2 4 4 4 5 5 7 9) stddev