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 laines = 3.0;
double acot = 5.0;

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

(2 + 8 / 3 + laines) / acot % 4

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 cunde = 8;
double sounghee = 4.0;
double ui = 1.0;
double plar = 4.0;

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

cunde > 1 || 6 == 0 || 7 != sounghee || ui == plar == (1 != 5)

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 (1ne2-dri7-apmm-0n6)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1db7-pdat-qwyn-iekj-f)