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 ca = 1.0;
double kelad = 4.0;
int erso = 7;
int gudsqan = 2;
double ar = 4.0;

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

7 * ca + kelad * erso / gudsqan + ar - 5

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 sipen = 2.0;
double cer = 5.0;
double fosplent = 1.0;
boolean trengnuc = false;
double haphmir = 2.0;

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

!(4 >= sipen) && 3 >= 8 != 5 <= cer && 5 == fosplent == !trengnuc != haphmir < 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" + 4 + 5 + 6 + "7"

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:

• While loops and for loops: Correct Solution (2uyf-wnmh-muya-4s1)
• Variable scope and lifetime: Correct Solution (ges8-vfv3-7fi1-wbnv)