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 priacs = 1.0;

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

1 / priacs + 0 + 1 % 6

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 ral = 3.0;
int ong = 1;
int frin = 8;
double wa = 3.0;
double ciount = 1.0;

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

ral > 1 || ong >= frin || wa > 1 && 0 >= ciount

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:

• Closures and event handling: Correct Solution (Ly4k-k74i-tcve-dz05)
• Variable scope and lifetime: Correct Solution (gfc0-chsv-n56q-a9uj)