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 i = 3.0;
double e = 2.0;
int giass = 4;

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

6 / i * e % giass * 0 - 5 + 9

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 a = true;
double ga = 4.0;
boolean ca = true;
boolean denkep = false;
boolean se = true;
boolean aje = false;

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

a || !(ga <= 8) || ca || denkep && se == aje

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 (gf4z-em6v-qi7d-ngns)
• Class declarations and object modeling: Correct Solution (17vk-L2sr-t7n7-y6vd-d)
• Booleans and conditionals: Correct Solution (5k0j-zmw6-mjwf-j1ai)