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 shre = 1;
double esposm = 1.0;
double buim = 3.0;
double vurhor = 3.0;

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

shre - (esposm - 4 - buim) - vurhor

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 cofac = 8;
double po = 5.0;
double sosint = 1.0;
int an = 4;
boolean gruou = false;

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

1 < cofac && (7 != po || sosint < an && gruou)

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

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 (wtp6-iisk-1hh3-rayd)
• Booleans and conditionals: Correct Solution (5oai-zqut-6zqk-mkad)