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 mopo = 3.0;
int ia = 8;
double ilcra = 3.0;

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

8 + (6 * 5 - mopo + 9 - 4 / ia * ilcra) + 8

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 wa = 1.0;
boolean strussscluc = false;
boolean ucchrenk = false;
double vul = 5.0;
int perol = 8;
boolean ent = true;
boolean sassal = false;

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

wa != 3 || strussscluc != ucchrenk || (vul < 1 == 7 <= perol == ent) != 4 < 0 == sassal

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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