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 cel = 4.0;
int phra = 8;
int caphpre = 1;
double spetre = 5.0;

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

5 / cel % phra % caphpre % 3 / 7 * 8 - spetre

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 thrusm = 3.0;
boolean ceur = true;
boolean fi = true;
double rard = 4.0;
double se = 3.0;
boolean icosm = true;

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

thrusm < 6 != ceur && fi == (rard == se) == !icosm && 5 > 9 && !(0 > 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 + "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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