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 i = 4;
double malshu = 1.0;
double pugress = 4.0;
double ha = 5.0;
double duss = 2.0;
double ieud = 4.0;
double testce = 1.0;

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

9 - (i % 6 + malshu * pugress / ha - duss % ieud % 5 + testce)

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 ongshress = false;
boolean caeis = true;
double od = 3.0;
double hiprou = 2.0;
double etrul = 2.0;
int puana = 1;

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

9 != 5 == (5 != 6) != ongshress && (caeis != 5 > od == (2 != hiprou) == 5 <= 1 == 8 < etrul != puana >= 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 + 8 + 9 + 10

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:

• Booleans and conditionals: Correct Solution (5jm4-3zds-dgn5-9vdg)
• Static and runtime types: Correct Solution (wtwu-qe3c-1ffz-wpqz)