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 esmglud = 4;
int peudplod = 2;
double pel = 1.0;
double o = 5.0;
double tir = 4.0;
int joatret = 9;

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

(esmglud % peudplod % 4) - pel * o * tir % 4 % joatret

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 sti = false;
double em = 5.0;
int di = 9;
boolean omo = true;
boolean io = true;
boolean trentqen = true;
boolean gless = false;

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

sti && 0 == em && 8 >= di && omo == io && trentqen != gless

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:

• While loops and for loops: Correct Solution (ugo1-Ld1j-3gmz-nu)
• While loops and for loops: Correct Solution (2xzx-4yw3-4wgs-kjj)