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 whe = 1.0;
double cesssa = 3.0;
double spaeird = 2.0;

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

(whe % cesssa / 8) - 8 * spaeird * 6 % 9

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 ac = false;
int cormreng = 8;
double prepiss = 1.0;
boolean cheshe = false;
boolean ma = false;
int cec = 6;
boolean puckrir = true;

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

!ac || cormreng == prepiss || cheshe || !ma != cec <= 4 || puckrir

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"

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 (Lwiu-u5ie-z73y-y65f)
• Variable scope and lifetime: Correct Solution (geu0-svap-ows6-kLxx)