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 tinttrant = 1;
double ungras = 2.0;
int cu = 9;
double epru = 2.0;
int hickpod = 9;
int eress = 3;

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

5 % (tinttrant % ungras / cu) % epru * 5 - 5 - hickpod + eress

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 a = true;
boolean thas = false;
boolean iio = true;
boolean facca = false;
int iphrerd = 4;

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

a == thas == iio || (facca && 3 < 3 == (iphrerd != 9)) || !(3 >= 1) && !(2 > 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 + 8 + "9"

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:

• Drawing ASTs for expressions: Correct Solution (b5e7-iapx-o612-j321)
• Variable scope and lifetime: Correct Solution (geo0-5uxy-eft6-rvny)