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 voss = 2;
double biciar = 1.0;
double rorstiu = 1.0;
int plar = 5;

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

(3 + 0 + voss * biciar % rorstiu / 2) + 2 * 3 * plar - 3 - 2

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 vi = 9;
double dokin = 4.0;
boolean piaspo = true;
boolean colast = true;
boolean en = false;
double rixpra = 5.0;
int satlon = 2;

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

vi == 3 == dokin >= 1 == piaspo == colast && 3 >= 7 && 1 != 1 && en != 2 > 6 == rixpra < 9 && satlon != 7

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

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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