Drawing ASTs for expressions: Correct Solution

For each of the Java expressions below:

• Draw an AST for the expression.
• Show how the expression evaluates at each node in the tree.

Be sure that your tree accurately reflects how Java would evaluate the expression.

Part 1

Given the following variables:

double phehan = 2.0;
int moupuck = 4;
double an = 5.0;
int od = 8;

...draw the AST and evaluation results for the following expression:

8 * phehan * moupuck - an - od * 6

Solution

Things to double-check in your solution:

• Do you have the left and right branches on the correct side?
• Did you indicate the difference between ints and floating point values?

Part 2

Given the following variables:

boolean raddo = true;
double keng = 5.0;
int suarsjio = 1;
int seos = 3;
double wirder = 1.0;

...draw the AST and evaluation results for the following expression:

!raddo || keng != 2 != suarsjio < 0 || 7 == 2 != seos > wirder

Solution

Things to double-check in your solution:

• Does your tree correctly reflect the precedence of && and ||?
• Did you correctly show short-circuiting? (That is when the right branch of && or || is never evaluated because the left branch already determines the answer.)

Part 3

Draw the AST and evaluation results for the following expression:

0 + 1 + 2 + 3 + 4 + "5" + 6

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

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