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 cio = 3.0;
double seasna = 3.0;
int eoc = 2;

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

1 - cio - 2 % seasna / 3 - 0 - eoc * 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 da = true;
int ka = 1;
int luss = 6;
double sqen = 5.0;
int chliantta = 9;
double priono = 3.0;
boolean gri = false;

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

da || ka > 5 == 6 > luss != (2 != 7) != sqen >= chliantta && 2 > priono || gri

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 (Lwko-i7ty-mfe4-je9d)
• Static and runtime types: Correct Solution (wtns-35sp-gh40-acid)