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 iourks = 8;
int icsher = 8;
double xieprous = 3.0;

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

iourks % 2 / 9 - 8 - icsher * xieprous / 7

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 ge = 4.0;
double os = 5.0;
boolean el = false;
int wess = 9;
int eac = 2;
double dessmaer = 5.0;
int fes = 1;
int neshgi = 9;

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

ge >= os && el || 9 >= wess && eac != dessmaer || !(fes < neshgi) && 5 <= 7

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)

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:

• Variable scope and lifetime: Correct Solution (gf6u-b47f-i6ts-uw8L)
• Class relationships: Correct Solution (re7L-54th-wpcr-r49h)