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 sa = 5.0;
double tacliss = 3.0;
int preou = 2;

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

sa % 8 % 4 - 0 / 3 * tacliss % preou

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 neltood = false;
double iodphio = 5.0;
int veoupan = 1;
double fiss = 4.0;
double sisto = 2.0;
double scri = 5.0;

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

neltood != (0 != iodphio) && !(4 < 0) && !(7 < 9) || veoupan == fiss == (sisto != scri)

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:

• Booleans and conditionals: Correct Solution (5isx-p49L-Lvhd-pguu)
• Closures and event handling: Correct Solution (Lyds-4pLr-jj0u-mmah)
• Booleans and conditionals: Correct Solution (5hoL-uasd-nxc2-bds9)
• While loops and for loops: Correct Solution (1ngd-crqg-eair-4jh)