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 stranio = 2.0;
int cidish = 4;
double sprar = 3.0;
double im = 4.0;
int apriod = 3;

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

8 * stranio - cidish - sprar % 7 % im + apriod

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 fre = 5.0;
int ti = 9;
int aimast = 6;
double revou = 1.0;
int strasmiat = 4;
int biarpre = 7;

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

1 <= fre == ti < aimast && (4 > revou || 9 != 9 || strasmiat > 8 != 4 < biarpre)

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)

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 relationships: Correct Solution (rLt1-3Lm9-k1fi-kf3s)
• Class declarations and object modeling: Correct Solution (17ru-o5p1-c23s-7vtp-0)