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 gurpsua = 3.0;
double dofost = 5.0;
double prunpel = 4.0;

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

9 / 6 - gurpsua + 8 * dofost / 3 % prunpel % 2 % 5 * 9

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 ar = 5.0;
boolean tinroud = false;
boolean bentror = false;
double adi = 3.0;
int amud = 5;
int bi = 1;
int thi = 9;
double i = 4.0;

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

ar > 1 != 8 < 6 != tinroud != bentror == 0 > 9 || adi != amud != (bi == thi) || 6 > 6 != 7 > i

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 + "10")

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 relationships: Correct Solution (rhwk-acox-cdfo-zngb)
• Variable scope and lifetime: Correct Solution (gez4-efns-ww99-Ly1y)