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 phow = 1;
int fe = 6;
double e = 4.0;
int pla = 8;
double ro = 3.0;

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

phow - fe + 1 + e / 0 - 6 * 2 * pla % 3 * ro

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 trelldirst = 5;
int ma = 3;
boolean bodecs = true;
double crernponn = 2.0;
int mabia = 2;
boolean ori = false;
double on = 3.0;
double bedra = 3.0;
int harme = 7;
double ud = 1.0;

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

trelldirst == ma == bodecs != (5 != 4) != (5 == crernponn) == mabia < 5 && !ori && on > bedra || 1 > 8 != harme > ud

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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