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 lalge = 2.0;
int gaemco = 7;

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

(7 * 2 / lalge % 1) + gaemco

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 nu = 5;
int a = 8;
double iser = 3.0;

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

6 != 5 || nu >= 8 && 4 >= 7 || a <= iser

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"

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 (xs0m-sw7w-bwkz-ie)
• Variable scope and lifetime: Correct Solution (genc-hr7z-y8pp-zqqi)