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 etsiang = 1;
int bloling = 1;
double asphaup = 5.0;

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

(etsiang % 1 % 8 + bloling) * asphaup / 8 - 0

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 ruersi = 1.0;
boolean bueda = false;
double esm = 3.0;
int lenont = 8;
boolean lintwhu = true;
boolean wigh = false;

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

(4 >= ruersi && !!bueda != esm > lenont) == lintwhu || 6 != 5 != wigh

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

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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