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 duph = 2;
double trar = 2.0;
double xar = 1.0;

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

5 * 8 / 5 / duph - 0 * 3 - 3 + trar % xar - 3 - 1

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 cleonso = 1;
double di = 1.0;
int eobam = 7;
boolean a = false;
int chosm = 4;
boolean dipra = true;
int huhan = 2;
double vogiomp = 2.0;

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

4 == cleonso != ((!(di != 6)) || eobam <= 9 != a == (chosm != 0) || 0 < 9 != dipra) == (2 == 0) || !(1 == huhan) || 5 == vogiomp

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 + 10 + 11

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 (wtwb-0enx-4mu5-0k2k)
• Class relationships: Correct Solution (rgxf-gdj5-7xbk-sden)