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 er = 1;
double posssier = 1.0;
double cel = 2.0;
double caud = 1.0;
double fio = 3.0;
int glelbiun = 5;
double fastan = 1.0;

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

er * (1 / 9 % posssier) - cel % caud + fio + glelbiun * fastan

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 soung = true;
int hi = 5;
int be = 7;
boolean scutuss = false;
boolean farur = false;
int mallal = 9;
double miacha = 3.0;

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

soung && hi <= be || scutuss != farur && 6 != mallal && 0 < miacha && 0 < 9 && 3 > 1

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"

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:

• Drawing ASTs for expressions: Correct Solution (az7e-mr8k-4ypd-67gf)
• Class declarations and object modeling: Correct Solution (17wt-f89a-rpaq-co28-1)