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 oved = 1;
double co = 3.0;
double e = 2.0;

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

7 + oved / (4 + co) - e

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 psaeo = 2.0;
int te = 4;
int piosstre = 3;
int swirtmel = 1;
double ix = 4.0;

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

!(1 <= 4) || (6 != psaeo && te != piosstre || swirtmel == ix)

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

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

Related puzzles:

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• Drawing ASTs for expressions: Correct Solution (b576-x9dn-5zLo-ujdi)