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 hiod = 7;
double ei = 4.0;
double puo = 2.0;

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

7 - hiod + (ei + 1 / puo)

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 clu = 5.0;
double vaedlic = 3.0;
boolean o = true;

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

(4 != 6 && clu >= vaedlic && o) || 1 >= 6

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 (Lxqi-haho-g2eq-e8wy)
• Variable scope and lifetime: Correct Solution (gf9z-do6f-40vm-hxxo)