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 hipin = 5.0;
double heic = 5.0;
double te = 1.0;

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

hipin * 3 % heic + te

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:

double bue = 5.0;
double thiphred = 1.0;
int qoses = 3;

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

bue >= 3 && 6 > thiphred && qoses < 7

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"

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:

• Class declarations and object modeling: Correct Solution (17ti-7f1n-soes-vs0L-g)
• Static and runtime types: Correct Solution (wtmp-ucdf-7t91-w9q6)