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 ecral = 2.0;
int neis = 1;
int ne = 8;
double degplai = 3.0;
double cleabaus = 3.0;
int poushe = 7;
double endo = 3.0;

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

1 % ecral / neis + 3 * ne - 2 + degplai * cleabaus - 5 - poushe / endo

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 spinpod = 3.0;
double houdmas = 1.0;
int hecras = 4;
int cemeng = 1;
boolean rosmdron = false;
double munnirds = 3.0;
boolean essrof = false;

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

spinpod <= 0 && houdmas != hecras && 0 <= 2 == !(4 < cemeng) && 3 >= 3 && (rosmdron != 9 <= 6) || 7 == munnirds && 7 <= 3 != essrof

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 + 11

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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