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:

int u = 8;
double pism = 4.0;
int priais = 7;
int gastar = 5;

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

(4 / u) / pism - priais + gastar

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 geenfrax = 1.0;
boolean pse = true;
int pleght = 1;
double fii = 5.0;

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

(!(geenfrax > 6) && pse || 1 != 7 || pleght == fii)

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

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:

• Booleans and conditionals: Correct Solution (5mth-spcv-ov9f-6e7t)
• Class declarations and object modeling: Correct Solution (17vy-usvi-w5L4-1a7f-p)