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 bilto = 4.0;
double eposm = 3.0;
double phitou = 4.0;
double a = 5.0;
int chereng = 8;
double shoustid = 1.0;
int su = 9;

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

bilto % eposm + 4 / phitou * 6 * a * chereng - 2 * shoustid / su

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 thior = 5;
double eiss = 2.0;
boolean tiswa = true;
int cula = 1;
int clur = 3;
double fuscrur = 3.0;
int o = 7;

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

1 >= thior && !(eiss < 0) == !tiswa == 7 >= 0 || cula <= 0 || !(clur < 2) != (3 != 5) || 4 <= fuscrur == o >= 2

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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