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:

double ori = 4.0;
int phou = 7;
double mo = 2.0;
int humo = 5;
int oon = 2;
int psanre = 9;

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

ori + phou + mo - 2 / 9 - humo + (oon - psanre)

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 hul = 1.0;
double pao = 2.0;
int cechdir = 1;
double sepheu = 5.0;
boolean depos = false;
double peunchos = 1.0;
double rass = 4.0;

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

(hul < pao && !(cechdir != 5) || !(sepheu > 8) || depos && 6 >= 0 || 1 <= peunchos || rass <= 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:

• Drawing ASTs for expressions: Correct Solution (b4oe-723w-bx6p-g4vo)
• Closures and event handling: Correct Solution (Lzfz-6rcf-96id-121z)