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 on = 5;
int stial = 5;
double io = 3.0;

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

(on + 6 / stial) * 7 * 1 - 2 / io

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 etse = true;
boolean spes = false;
boolean clasmick = true;
int midlint = 9;

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

7 > 3 == etse || !spes && (0 != 6 != clasmick) == (midlint == 3)

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 (wt9q-y9eb-gfn1-65uc)
• Static and runtime types: Correct Solution (wtqv-3r2w-yc63-mhii)