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 denhut = 4;
double id = 1.0;
double ecda = 5.0;
double eban = 1.0;

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

8 / denhut - id + 3 * ecda * 7 - 0 % eban

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 ussmel = true;
boolean iss = false;
boolean ed = false;
boolean u = true;
int sissbis = 8;

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

ussmel == iss || ed || 4 > 0 || u || sissbis == 2 || 6 != 9

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

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:

• Closures and event handling: Correct Solution (LwLi-ycxz-94c1-tt84)
• Booleans and conditionals: Correct Solution (5h8q-4oph-0Ltb-tems)