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:

int cheest = 1;
double ochrung = 5.0;
int sostan = 5;
double eu = 4.0;

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

5 % cheest / ochrung * (1 + 8 / sostan % eu)

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 manlong = 2.0;
double phront = 1.0;

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

(9 != manlong || !(!(1 != 8)) == 3 >= 8 || 4 != 1 || 9 >= 7 == phront < 1)

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:

• Variable scope and lifetime: Correct Solution (gf0q-5w0e-kz1x-gfvj)
• Booleans and conditionals: Correct Solution (5mq6-mfm4-btsp-zcyj)