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 vess = 3;
double holan = 4.0;

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

5 - vess * (8 - 8) % 2 / holan

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 issor = 7;
int vussnung = 9;
boolean ca = false;
boolean aintplist = false;
boolean tosmposs = true;

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

9 <= 4 == (issor <= vussnung == ca && aintplist) && !tosmposs

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)

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:

• Class declarations and object modeling: Correct Solution (17sg-hzik-s2x0-drkb-4)
• Variable scope and lifetime: Correct Solution (geq3-r5ca-mvxy-aetb)