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 slephta = 8;
double ca = 5.0;
double jemos = 4.0;
int ne = 1;
int lonoc = 9;

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

slephta / ca / (3 / jemos) * ne * lonoc + 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 ohscrot = 5.0;
double missrin = 1.0;
double lungshast = 3.0;
boolean odrad = true;
boolean blung = false;

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

4 != 1 == ohscrot > 6 != 8 >= missrin && 8 >= lungshast != odrad || blung

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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• Class declarations and object modeling: Correct Solution (17t9-kais-pnfi-k5ve-o)
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• Booleans and conditionals: Correct Solution (5L44-s2qf-pkjc-5teb)