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 chiied = 7;
int co = 8;
double gedca = 2.0;
double ainalm = 2.0;
int pe = 4;

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

chiied + co / gedca / 5 + ainalm + 9 + 2 % pe

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 masqe = 5.0;
boolean qoss = false;
boolean treng = true;
boolean ste = true;
int etris = 2;
boolean wapre = false;
double birmang = 3.0;

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

(masqe >= 4 != !qoss && treng && ste) && etris >= 1 == wapre == birmang >= 9

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:

• Closures and event handling: Correct Solution (Lvx6-fc17-j8eu-v6md)
• Static and runtime types: Correct Solution (wt8h-281a-mvro-fc9h)