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 o = 7;
double priar = 4.0;

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

o % 6 % 4 % 7 + (9 % priar * 6) % 2

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 cheshwiorn = 1.0;
int sa = 4;
double fonass = 2.0;
boolean odvum = true;
boolean fliti = false;
int hioong = 9;

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

8 == 1 != (cheshwiorn < sa && 2 > 5 || 9 <= fonass) == odvum || fliti == (hioong != 6)

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 (wtxv-i15b-nwq5-bsiq)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d98-hgy4-6nwd-dt7j-w)