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 ro = 1.0;
double mex = 3.0;
int ce = 8;
double prebrest = 1.0;

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

(ro % 7 % mex * ce) % prebrest * 5

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:

boolean taas = true;
boolean headol = true;
int rer = 9;
double edhe = 1.0;
double mi = 1.0;
int primmo = 1;

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

!taas && (headol != rer <= 1 == edhe < mi != primmo <= 4)

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?

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