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 pra = 3.0;
double ekspet = 3.0;
double en = 2.0;
double cas = 1.0;

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

5 / pra * 1 % ekspet / 9 / en % cas

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 hosm = false;
double prinic = 1.0;
int dentlax = 4;
int ruint = 4;
int tricfom = 4;

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

(hosm != (!(7 != 2)) || 3 >= 2 != (prinic == dentlax) != (!(8 == ruint))) && tricfom == 2

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

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 (17wq-ryv2-izn7-m157-c)
• Static and runtime types: Correct Solution (wtrt-da51-bu7q-4mxr)