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 iiwhe = 4.0;
double wirthcoc = 4.0;
double eghtsu = 2.0;
double smoessjil = 2.0;
int id = 9;

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

iiwhe - wirthcoc / eghtsu / 5 / 5 * smoessjil + 4 / 8 * (2 % id * 6 - 4)

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 eheud = 9;
boolean fiandro = true;
double di = 2.0;
double miobnont = 3.0;
int stollqo = 5;
boolean binras = false;
boolean a = false;

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

(3 >= 5 != (5 != 1) == 0 >= eheud || 3 > 9) && fiandro || 7 > 2 && di > 9 && miobnont == stollqo == binras && a != (7 == 1)

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" + 11 + 12

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

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