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 phecpo = 2;
int oli = 9;
int zacra = 9;
int heoun = 2;

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

9 - 2 % 1 * phecpo + 6 % oli % zacra / heoun

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 iss = 3;
boolean badrion = false;
int tawheaet = 5;
boolean untsa = true;
int runda = 8;
boolean censpousm = false;
int xiing = 9;

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

8 != iss != badrion && tawheaet > 6 == untsa != !(runda <= 4) || censpousm != 6 <= xiing

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 (gf23-x245-k9e1-cf1s)
• While loops and for loops: Correct Solution (24ga-o08u-bnur-mav)