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 lanics = 5;
double prousscean = 1.0;
int so = 5;
double chavent = 3.0;

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

(lanics % prousscean * 9 / so / 5) % chavent

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 te = 4;
int aingse = 2;
double drem = 5.0;
double stemor = 5.0;
double ninto = 5.0;

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

te == 6 && 1 == aingse && drem < stemor == (5 == ninto) != 9 < 7

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

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 (1sh2-bkmk-kebm-30q)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d9z-2hy1-86vf-eryh-o)