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 glinvoss = 2;

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

2 - 1 * 5 + glinvoss % 1 / 9 + 9

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 alljess = 1.0;
double prenhir = 4.0;
boolean ird = true;
double esm = 2.0;
boolean smoch = false;
int prenpron = 8;
boolean oelfri = true;

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

alljess >= prenhir || ird || 0 >= esm || smoch != prenpron >= 5 == oelfri

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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