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 ptou = 1;
double de = 2.0;

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

6 + (7 / 3 + 5 + 6) + 8 / ptou % de * 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:

boolean hiqe = true;
double un = 4.0;
int giobri = 4;
boolean zunt = true;
int binphlal = 7;
double triwoss = 1.0;
int clen = 1;

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

hiqe != 9 <= un && 4 != giobri == zunt || binphlal > 3 == (triwoss > clen || 3 < 6 == (3 != 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" + 5 + 6 + 7 + 8 + 9

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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