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 drund = 2.0;

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

4 * 0 % drund * 7 % 7 % 3 * 9

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 grem = 3;
double auprou = 3.0;
int iss = 6;
int cisod = 1;
double cae = 1.0;
boolean soothio = false;
double eclal = 1.0;

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

grem == auprou || 3 == 1 == iss > 7 && cisod < cae || !!soothio != 1 < eclal

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:

• Static and runtime types: Correct Solution (wtv6-o5pj-gawj-7vt6)
• Static and runtime types: Correct Solution (wtgv-nxfn-pwso-6med)