9.2. Worked Example: Arrays - Traverse¶

Subgoals for Evaluating Arrays

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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;

SG1: Set up array from 0 to size-1

alpha = new int[10];

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).

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.

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:

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