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 riblo = 5.0;

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

5 - 3 - (riblo / 0)

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:

int cio = 9;
double bi = 3.0;
double mi = 2.0;
double eothpa = 5.0;

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

1 > cio || bi < mi || 0 <= eothpa

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:

• Variable scope and lifetime: Correct Solution (geu8-gckz-pdcy-etw6)
• Drawing ASTs for expressions: Correct Solution (azvc-9b4e-Lp66-84rk)