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 om = 5.0;
int phismiort = 2;

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

1 % (om / 8 / 6) / phismiort

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 astent = 4.0;
double li = 2.0;
double ploon = 2.0;

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

(3 > astent && 5 < li && !(1 != 5)) || ploon >= 5

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:

• Class declarations and object modeling: Correct Solution (17sm-pcsc-3hj0-633s-n)
• Static and runtime types: Correct Solution (wtub-iyug-phy8-6o1o)