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 dudo = 1.0;
double rindpar = 2.0;
double thei = 5.0;
int ba = 3;
int o = 8;

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

0 - dudo * rindpar * 9 + (thei / ba + 9 * 7) + 0 * o - 7

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 marfed = true;
boolean cic = false;
boolean dause = true;
int re = 9;
boolean hengmiang = false;
boolean cicio = false;
boolean puar = false;

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

marfed != cic && dause || !(0 >= 2) == (2 != re) || 7 == 1 != (3 == 4) != hengmiang == cicio != puar

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 + 11

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:

• Static and runtime types: Correct Solution (wtkb-c3b4-ddpf-uzz5)
• Class declarations and object modeling: Correct Solution (17xb-aod1-87o1-4k3j-6)
• Closures and event handling: Correct Solution (Lwx2-f6hq-pas2-mfb5)