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 gintsol = 5;
int towar = 4;
int fiol = 6;

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

(gintsol / 3 * towar - 5 / 6 - 8 - fiol - 8) % 8

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:

int mier = 7;
int ur = 8;
double candcerk = 5.0;
double trimi = 3.0;
int idfliass = 6;
double ussmint = 2.0;
double er = 4.0;
double eiism = 1.0;

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

mier != 5 && (1 <= ur || !(3 == 1) && candcerk >= 1 == trimi < 4) != !(6 < 0) == idfliass >= ussmint != !(er < eiism)

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

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:

• Static and runtime types: Correct Solution (wteo-x9m1-ter1-L0a1)
• Class relationships: Correct Solution (rkpe-93e0-kiL3-iLdx)