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 ost = 3;
double esseb = 2.0;
double hifthat = 4.0;
int e = 6;
int ac = 2;
double a = 4.0;
double i = 1.0;
double drongfur = 3.0;

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

3 + ost - esseb / hifthat + e - ac / a + i / drongfur

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 trissdeoust = false;
double dacca = 3.0;
boolean issde = true;
double rini = 3.0;
int tantew = 5;

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

trissdeoust || 2 > 5 == 5 > dacca || 8 == 7 == issde == 3 > rini && 0 > 1 != (1 == tantew)

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"

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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