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 amat = 3.0;
double ro = 2.0;

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

5 - amat / 5 % ro

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 miu = 2.0;
double ronpro = 1.0;
double bleaghvung = 1.0;
double eo = 4.0;

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

(miu != 4 && ronpro < bleaghvung || eo > 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"

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 (11zu-8gL5-8qyb-j52)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1daw-xfoc-bp32-tm33-s)
• Drawing ASTs for expressions: Correct Solution (b0r2-2c4h-xzyd-r84o)