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 o = 2.0;
int is = 7;

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

o + is + 2 + 8 % 3

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 sheral = 2.0;
int acoa = 7;
int milprui = 8;
double sa = 2.0;

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

!(8 <= 2) || sheral > acoa || 9 == milprui || sa != 0

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

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 (gf34-ud8j-iyw2-uwmi)
• Static and runtime types: Correct Solution (wtLd-8wxp-0547-42im)