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 ce = 2.0;
int ri = 6;
int ptisssor = 5;
double mo = 2.0;
double ichtess = 3.0;
double enthim = 5.0;

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

ce / ri % ptisssor / mo + 8 / 7 / 8 / ichtess + 8 - enthim - 5

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:

double giau = 1.0;
boolean vocem = false;
boolean eabun = true;
int i = 3;
int pimec = 5;
int engtre = 1;
int co = 6;

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

7 == 7 && giau == 7 != 1 <= 8 == vocem == !(6 > 1) != eabun == 0 <= i != !(!(pimec >= engtre)) == 6 >= co || 0 > 2

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 + 9 + 10 + 11

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 (2Lbb-31m9-v5ha-2iv)
• Booleans and conditionals: Correct Solution (5nek-wa27-eoqo-iku9)