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 bruss = 8;
double ipoi = 2.0;
double urscid = 2.0;
double ic = 3.0;
double trangs = 1.0;

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

bruss * ipoi + urscid / 0 - 9 * 1 / ic - 5 % 1 + trangs

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 inpatch = 2;
boolean mudbox = true;
boolean ebal = true;
double ti = 5.0;
double timses = 1.0;
boolean ohoof = true;
double en = 2.0;

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

4 != inpatch != (0 == 8) || mudbox != 5 > 6 || 3 >= 1 == ebal != ti < timses && ohoof && 5 >= en

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 + "9" + 10

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

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• Stack frames and objects (like the Idea Lab activity): Correct Solution (1da1-xew2-8mk3-g57w-4)