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 tro = 9;
int a = 8;
int me = 9;
int ofird = 8;

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

tro / 1 + 8 - a - me + 3 % 9 * ofird * 1 % 6

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 psiduk = false;
double eei = 2.0;
boolean diack = false;
double nel = 4.0;
boolean prubad = false;
int santiocs = 4;
double ia = 5.0;

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

!psiduk && 7 > eei == diack == (3 != nel) && !prubad || 1 < 0 != 6 <= santiocs || 6 != 6 != 9 > ia

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 + "10"

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:

• Drawing ASTs for expressions: Correct Solution (az2L-nsa8-fzh5-o6di)
• Closures and event handling: Correct Solution (Ly8k-j95c-hm8w-19en)