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 tes = 3.0;
double a = 2.0;
int mastla = 6;
double niam = 4.0;

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

tes + a / 3 / mastla % 1 / niam

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 ab = true;
int morkmen = 9;
double qalu = 5.0;

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

(6 >= 6 || ab != (!(4 == 4)) != morkmen <= 5 && qalu < 0)

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"

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:

• Booleans and conditionals: Correct Solution (5mpa-adb7-7vvk-pc9t)
• Closures and event handling: Correct Solution (Lw1s-50du-1bd7-edbq)