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 ti = 1;
int o = 7;
double steghtder = 1.0;
int e = 5;
int rii = 4;

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

3 - ti - 9 * o + steghtder / e + 2 + rii

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 medme = 2.0;
double qessial = 3.0;
boolean brirdstau = true;
int minpard = 7;
boolean ipre = false;

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

0 > 5 != !(3 > medme) && 0 <= qessial && !brirdstau && 4 != minpard && ipre != (5 == 7)

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:

• Static and runtime types: Correct Solution (wtj8-dkg5-yct9-3297)
• Booleans and conditionals: Correct Solution (5nbv-9mps-nxjw-vfca)
• Drawing ASTs for expressions: Correct Solution (b5ja-06ar-1j57-xqe0)