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 fep = 7;
int sqen = 2;
int le = 8;

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

fep + 1 % sqen % 9 % le

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:

boolean lami = true;
double ceuches = 1.0;
double litro = 3.0;
double sordec = 3.0;
int tirsent = 6;

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

lami && 9 > ceuches && litro > 9 && sordec != tirsent

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:

• Booleans and conditionals: Correct Solution (5jt5-rpwf-dn4s-wbkz)
• While loops and for loops: Correct Solution (33n9-xp0u-72y3-3up)