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 li = 8;
double butresm = 2.0;
double pe = 3.0;
int hootess = 2;
double nopin = 1.0;

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

2 * li / butresm - pe * 1 * 1 * hootess + 3 + nopin + 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:

int on = 1;
int pra = 4;
double nic = 4.0;
double tasteae = 4.0;
int sas = 2;
boolean ek = false;

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

on != 4 == pra > 1 != (!(5 <= 3) == nic <= 8 || tasteae == sas) || ek != !(8 >= 9) == 2 >= 4 != (!(2 != 3))

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:

• While loops and for loops: Correct Solution (14pe-2erg-r4s1-0L5)
• Drawing ASTs for expressions: Correct Solution (b407-p6bi-3zw1-grv3)