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 heif = 5.0;
int frerm = 8;
double shuss = 1.0;
int memir = 7;
int io = 2;
double pratpa = 1.0;

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

heif / frerm / shuss / 2 * (memir / io * pratpa) + 4

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 cral = 2.0;
boolean ro = true;
int ci = 8;
double bi = 2.0;
double prispsiod = 2.0;
boolean arsa = true;
double plar = 2.0;

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

2 >= cral || 9 <= 3 && ro || ci >= 4 && bi <= prispsiod != !arsa == plar <= 0

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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