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 icti = 4;
int muec = 1;

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

icti - 8 / muec * 9 - 0

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 iat = 3;
int o = 1;
double er = 2.0;
double chinslo = 4.0;

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

5 <= iat || 3 <= o && er != 3 && 9 > chinslo

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:

• Variable scope and lifetime: Correct Solution (ger4-py85-y06d-ay4s)
• Class declarations and object modeling: Correct Solution (17sa-61y7-ivwt-857e-3)