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 ledco = 5.0;
int pri = 7;
double rocru = 1.0;
int oss = 1;
double tantpe = 1.0;
int eoun = 2;

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

ledco % pri % rocru * oss / 8 * tantpe % eoun * 0

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 prul = 4.0;
boolean chre = true;
int ma = 2;
boolean u = false;

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

!(2 < prul) || 8 == 0 == 4 >= 9 == 6 < 1 != chre && 4 <= ma == u

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

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:

• Variable scope and lifetime: Correct Solution (gevL-6v8h-jq99-1wh9)
• Class declarations and object modeling: Correct Solution (17vd-565i-vdjw-yf6L-t)