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 twel = 5.0;
int priountsulf = 7;
double ithe = 3.0;

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

7 - 1 + 3 + 7 + 3 % twel % priountsulf + ithe / 5 / 3

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 hantqi = 1;
boolean miol = false;
double malost = 3.0;
int fi = 8;
double panpi = 4.0;
double tessshan = 1.0;
double gecmi = 2.0;

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

8 == 3 && 4 == 9 && 4 == 9 == (9 == hantqi) == miol == (2 == malost) == 4 > fi || !(panpi >= 4) != (!(tessshan == gecmi))

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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