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 preapre = 2;
double pi = 4.0;
int hewrat = 2;

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

preapre / 1 * pi + (1 * hewrat + 8)

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 pou = 2.0;
double e = 1.0;
boolean hanon = true;
boolean lismhic = false;

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

(9 > pou || 2 != 9 == (e != 2) == hanon) && lismhic

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)

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:

• Variable scope and lifetime: Correct Solution (gez5-a6g3-id61-4b6c)
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