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 stil = 6;
int me = 7;
double cogmer = 2.0;
double cepshal = 5.0;

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

(stil * me + cogmer % cepshal) / 7 * 8

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 ae = 2.0;
int ecork = 4;
double shas = 1.0;
int lopon = 2;
boolean jintpiss = true;
double bedthral = 4.0;

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

2 == ae != !(ecork < 3) || shas != lopon && jintpiss || 0 >= bedthral

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?

Related puzzles:

• While loops and for loops: Correct Solution (1mwe-6s57-7znx-qsf)
• Variable scope and lifetime: Correct Solution (geto-x0ri-0ozj-6xzs)