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 ad = 2;
double rontras = 1.0;

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

4 - 0 - ad % 8 % rontras / 3

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 edur = 2.0;
int aserm = 8;
int cedspil = 1;
boolean ma = true;
double ick = 5.0;
int rold = 7;
boolean enxned = false;

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

edur < aserm || cedspil >= 7 || ma || ick < rold && enxned

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:

• Closures and event handling: Correct Solution (Lz04-j1gL-vezc-35ju)
• Class relationships: Correct Solution (rkso-5s2v-v1u4-1hr7)