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 shorod = 5.0;
double fuouc = 4.0;
int misspe = 9;
int plos = 8;
double lelsie = 1.0;

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

5 + 3 % 7 + 3 * shorod * 3 * fuouc % misspe + plos + lelsie

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 ea = 9;
double plallclas = 5.0;
boolean uerbird = false;
double es = 5.0;
int veel = 2;
int dialo = 7;
int eit = 6;

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

ea == 0 && 5 >= 2 == 6 >= plallclas && !uerbird != (es == 9) == !(5 >= 9) == 2 < veel != dialo >= 4 != eit > 3

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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