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 ocen = 4.0;
double wanmurm = 2.0;
int ewi = 7;
double dre = 2.0;
double strird = 5.0;

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

6 - 4 % ocen + 5 + wanmurm - ewi * 3 % dre % strird

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 ven = 8;
double sios = 3.0;
double osmma = 4.0;
int trarpa = 2;
boolean biorgoc = true;
double hapmam = 2.0;
double couss = 3.0;
int ussfri = 3;

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

ven >= 7 || (9 <= sios == osmma > trarpa || biorgoc == !(hapmam > couss) && ussfri <= 1 == (7 == 2) || !(5 != 5))

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 + 8) + 9

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:

• Static and runtime types: Correct Solution (wtbu-n6d5-v6of-rvL2)
• Static and runtime types: Correct Solution (wtpr-hdm8-ybzd-6u2u)