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 ucnel = 3.0;

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

ucnel - 2 + 6 - 1

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 crerk = true;
boolean ehios = true;

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

crerk || (ehios || 3 != 4)

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

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:

• Static and runtime types: Correct Solution (wtcj-tw8h-pzba-nbbn)
• Closures and event handling: Correct Solution (Lvtt-L9t4-hsio-ifke)
• Drawing ASTs for expressions: Correct Solution (b14o-n72d-2uyx-hLxk)