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 triscil = 3;
double ta = 3.0;
double isfo = 2.0;
double maroar = 1.0;

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

triscil * ta + isfo / maroar / (7 % 4) * 4 / 2 * 0

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:

int bisess = 4;
int i = 6;
double ka = 3.0;
double pecsent = 2.0;
boolean mantleud = true;
double pelan = 2.0;
double emian = 5.0;

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

bisess <= i || ka != pecsent || 6 != 2 && mantleud != (1 == pelan) || 3 < 1 && 6 != 1 != 5 >= emian

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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