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 macdi = 3;
int iviss = 6;
int plusa = 8;
int em = 8;
double bir = 5.0;
double hasha = 3.0;

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

macdi - 8 - iviss / (plusa % em + 7 - bir / 3 / hasha)

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 riwic = false;
boolean asfot = false;
boolean flesnu = true;
boolean ioum = false;
boolean pnoassalt = false;

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

3 > 5 != riwic && (asfot || 5 > 7 != !(4 > 7) == flesnu) || !ioum == !pnoassalt

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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