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 scerme = 1.0;
int rehirt = 6;

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

(3 * scerme) % rehirt

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 oarm = 5.0;
int sintci = 5;

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

oarm >= 8 && sintci > 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

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 (gest-w6pj-3sce-bnx7)
• Class declarations and object modeling: Correct Solution (17wk-3gh0-4pcv-wt3g-L)
• Variable scope and lifetime: Correct Solution (geyo-4t5t-nzgi-nd2g)