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 ou = 1;
double a = 1.0;
double o = 3.0;
double focad = 3.0;
double an = 4.0;

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

1 - 2 + 3 + (6 - ou - 9 + a) * o - focad * an

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 swo = true;
int blomam = 6;
int u = 7;
double uige = 4.0;
boolean ceslass = true;
int ziemed = 3;
int sphi = 9;

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

swo && !(blomam >= u) != (1 < uige == (1 == 3) || !ceslass) == ziemed < 3 == sphi < 6 != 8 >= 9 == (3 != 5)

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:

• Class declarations and object modeling: Correct Solution (17uj-vxxq-itpv-bLpg-m)
• Class relationships: Correct Solution (rkrb-hrkh-rvw9-p04u)