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 pla = 5.0;
double tricsne = 4.0;

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

(1 / 1 / pla) * tricsne / 3

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 freae = 3.0;
double la = 2.0;
boolean semar = false;
int emis = 1;
int triler = 5;

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

!(freae <= la) || (semar && 4 < 8 && emis == triler)

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"

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:

• Variable scope and lifetime: Correct Solution (gfap-dnyL-a2k2-ncxw)
• Class declarations and object modeling: Correct Solution (17uq-3dbf-ganb-95wr-e)