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 itio = 4.0;
double chetpas = 3.0;
int pa = 4;
double firis = 4.0;

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

1 + itio - 4 / (6 - chetpas + 2 / pa) / 8 * firis

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 remtesh = true;
double bruicir = 2.0;
int casin = 6;
int miir = 8;
double micdong = 5.0;

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

remtesh || 5 > 6 == (4 >= bruicir != 5 < 5 == casin < 5 && !(7 < 0)) || !(3 >= 6) || !(miir < micdong)

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 + "7" + 8 + 9

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 (gezp-3s17-je34-5o3q)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d8g-nrxa-8g87-krf7-u)