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 virod = 1.0;
double olmim = 1.0;
int idceng = 3;
double stiapeack = 1.0;

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

7 / virod / olmim * idceng % 7 - 2 % stiapeack

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 methe = false;
boolean prenkseng = true;
boolean ie = true;

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

(!methe == 4 >= 5 || 8 > 4 || !prenkseng != ie && 9 > 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" + 6 + 7

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:

• Stack frames and objects (like the Idea Lab activity): Correct Solution (1dbg-yt4v-gk1n-amuq-k)
• Closures and event handling: Correct Solution (Lz2q-rfqd-cggn-atdx)