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 dithprot = 5;
double ou = 4.0;
double sphon = 2.0;
double cepilth = 3.0;

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

(1 / 2 + 8) / dithprot * ou + sphon - cepilth * 6

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 whibu = 4.0;
boolean esluck = true;
int plebast = 6;
int preng = 6;
double tenic = 2.0;
boolean re = true;
int cestae = 8;

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

!(2 == whibu) && esluck != plebast > preng || 6 <= 3 != (!(tenic != 9)) == re != cestae >= 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"

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 (wtpb-rwfj-2rum-i34L)
• Class declarations and object modeling: Correct Solution (17v5-bj44-p5Lg-nonv-3)