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 funsba = 2.0;
int pra = 9;
double cardu = 1.0;
double im = 2.0;

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

funsba + pra * 4 - cardu % 4 / 6 - 6 / 5 - im

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 neess = 5.0;
boolean lul = false;
boolean voa = true;
double trarunt = 3.0;
int poulur = 3;
boolean reenkism = false;

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

3 < 3 == 4 <= neess == (2 == 4) && lul != !voa && !(!(1 >= trarunt)) == poulur < 7 || reenkism

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 + "9"

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:

• While loops and for loops: Correct Solution (33n9-xp0u-72y3-3up)
• Variable scope and lifetime: Correct Solution (gf4k-s4d4-my89-j6mp)