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 ninbel = 9;
double ri = 2.0;
int um = 6;

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

ninbel + 5 * (5 - 8) % ri % um

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 sanen = 3.0;
int idcor = 9;
boolean ouss = true;
boolean olning = true;
double whicto = 3.0;
double sotseurt = 4.0;
boolean ehod = false;

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

(sanen <= idcor || ouss && olning || whicto <= sotseurt) || ehod

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?

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