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 nadpol = 1.0;
double threntli = 5.0;
double caspiur = 3.0;

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

nadpol * 3 * (threntli / 6 - 4 % caspiur) * 3

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 khassunt = 2.0;
int zom = 8;
int iormsciod = 7;
double besssco = 3.0;
boolean dimem = true;
int cu = 9;
int orrourt = 8;

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

khassunt <= zom || (2 > 2 == (iormsciod != besssco) != dimem != !(!(cu >= 4))) == 6 <= orrourt

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

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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• Closures and event handling: Correct Solution (Lzky-bd25-psf1-exze)
• Variable scope and lifetime: Correct Solution (geox-3m4s-71k2-ykik)