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 comen = 5;
double snejan = 4.0;
int immoack = 9;
int prodrent = 6;

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

comen % snejan * 7 / immoack - 4 / prodrent % 8 - 0

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 napo = false;
int a = 3;
boolean spu = true;
boolean pelco = true;
double hi = 3.0;
int veino = 6;
double leltra = 4.0;

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

napo && 0 > 4 && 0 != a == spu != pelco == !(5 <= hi) != (!(veino != leltra))

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:

• Booleans and conditionals: Correct Solution (5nkg-ztnx-hf4c-v8kc)
• Closures and event handling: Correct Solution (LyLi-yo9a-ge79-yjjv)