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 ix = 7;
double od = 4.0;
int oo = 2;
double hidde = 2.0;
int ic = 7;

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

ix / od * oo / 3 + hidde % ic * 8 % 2

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:

int io = 8;
int sont = 7;
boolean pio = true;
double slea = 2.0;
double rioac = 2.0;
int proungfi = 8;

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

8 != io != 6 > sont == pio || slea <= 0 || rioac >= 7 != 0 >= 5 != proungfi > 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) + "5" + "6" + 7 + 8

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:

• Variable scope and lifetime: Correct Solution (gf1h-w97k-dufk-m0td)
• Drawing ASTs for expressions: Correct Solution (az9t-zdzi-aqds-m70t)