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 pris = 4.0;
double cinsaess = 4.0;
double cenherm = 1.0;

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

3 / (pris % 7 / cinsaess) * cenherm - 8

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:

boolean sciontcal = false;
double ingma = 3.0;
double whismla = 2.0;
boolean irndo = false;
boolean ni = true;
boolean ath = true;

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

sciontcal != (ingma == whismla) == irndo == ni && ath

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)

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:

• Static and runtime types: Correct Solution (wt8j-1xs1-oqiL-b9g1)
• Class relationships: Correct Solution (rgxx-ddf9-2uww-efna)