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 ano = 1.0;
double bifesh = 4.0;
int phegleing = 1;
int pinint = 9;
double irmdot = 5.0;
double uin = 4.0;
double heg = 5.0;

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

ano % bifesh % 2 * phegleing * (pinint + irmdot + uin * heg)

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 dehas = 2.0;
int sturer = 3;
double plec = 2.0;
int e = 6;

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

!(9 <= 4) != 6 >= 0 == ((6 == 3) == 1 > 6 == dehas > sturer) && 3 != plec != (!(e == 9))

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

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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• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d9s-3vvi-jyao-tbub-1)
• Booleans and conditionals: Correct Solution (5igc-r3wb-xqgk-wm7v)