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Subgoals

Section 11.3 Worked Example: Arrays - Traverse

Subgoals for Evaluating Arrays.

  1. Set up array from 0 to size-1
  2. Evaluate data type of statements against array
  3. Trace statements, updating slots as you go
    1. Remember assignment subgoals

Subsection 11.3.1

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Problem:
Given the initialized array:
int [] alpha;
Evaluate these statements and determine the value of all variables. If any error occurs, give the reason.
alpha = new int[10];
for (int i = 0; i < 10; i++)
alpha[i] = i * 1;

Subsection 11.3.2 SG1: Set up array from 0 to size-1 

alpha = new int[10];
Figure 11.3.1.
  • alpha is declared as an array of int
  • This statement allocates 10 slots for integers (first line are values, second line are indexes)
  • Notice that the largest index is 9 (size of 10 minus 1).

Subsection 11.3.3 SG2: Evaluate data type of statements against array 

for (int i = 0; i < 10; i++)
   alpha[i] = i * 1;
  • This loop has index i go from 0 to 9 (< 10) by increments of 1.
  • Then the value i * 10 is placed into the position alpha[i].
  • All of the array indexes are within the bounds of the array (0 – 9) and all values being assigned (10-90) are valid integers and can be stored in an integer array.

Subsection 11.3.4 SG3: Trace statements, updating slots as you go

We will evaluate the first two statements:
for (int i = 0; i < 10; i++)
   alpha[i] = i * 1;
The resulting array is:
Figure 11.3.2.

Subsection 11.3.5 Practice Pages

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