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 ke = 5.0;
double shis = 5.0;
int prescis = 9;
int noui = 4;
int ismuss = 3;

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

9 / (5 * ke % shis) * prescis - 8 * noui / ismuss

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 magess = 2.0;
int ceim = 3;
double iolil = 1.0;
boolean ciapon = true;
boolean laltra = false;

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

4 >= 1 != 7 <= 4 && (1 < 6 != (7 == magess)) == ceim > iolil && ciapon == laltra

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

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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