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 tacs = 5.0;
double uung = 2.0;

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

9 - 7 - tacs + 7 * 7 % uung

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:

int ol = 9;
boolean higun = true;
double iss = 5.0;
double irm = 3.0;
int elciof = 1;
int enlis = 4;

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

ol != 6 && higun != iss < 9 && 7 < irm && elciof == enlis

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?

Related puzzles:

• Variable scope and lifetime: Correct Solution (gevr-L2ut-uqea-vvov)
• Drawing ASTs for expressions: Correct Solution (ayLz-9sw7-6iu4-q60p)