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 ti = 3.0;
double mo = 4.0;
int chiiss = 7;
int phe = 5;

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

1 / 9 / ti % 9 + mo - 5 / chiiss / 7 - 9 + phe

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 feto = true;
boolean e = false;
double epsik = 3.0;
boolean ocit = true;
double licent = 3.0;
double ul = 5.0;
int chli = 4;
int rurac = 1;

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

feto != !e != 3 <= 0 != !(4 > 5) != !(5 < epsik) == ocit != (licent == ul) && 8 > 4 || chli == rurac

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" + "10"

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:

• Booleans and conditionals: Correct Solution (5n7w-o6rp-47hc-bsrz)
• Class declarations and object modeling: Correct Solution (17wj-7a8u-eq4s-uvhv-v)