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 bocrol = 5.0;
double biel = 5.0;
int preniong = 9;
double perte = 4.0;

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

bocrol / 3 + 8 - biel / preniong - 1 + perte

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 pof = 1.0;
int schoa = 9;
boolean elim = true;
int ne = 2;
int pucs = 7;
boolean om = true;

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

pof >= schoa && elim != (ne == pucs) && 8 > 1 == om != 7 > 6

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

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

Related puzzles:

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