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 za = 2.0;

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

5 % 8 + 2 / za / 2

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 tiandap = 7;
double saca = 5.0;
boolean ivi = false;
double asu = 3.0;
double hiswunt = 4.0;

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

tiandap <= 1 && !(saca != 8) && (ivi && asu >= hiswunt)

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:

• While loops and for loops: Correct Solution (34zh-bsvt-4rvp-dsg)
• Class declarations and object modeling: Correct Solution (17vc-q6g3-anwr-uhwt-d)