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 o = 2.0;
int ciureasm = 6;
int dictish = 9;

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

o % 8 * ciureasm / 3 % 1 - 5 - 7 / 2 - 8 % dictish

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 olbri = false;
int lal = 1;
double hodspos = 4.0;
int haph = 7;
boolean buintscod = true;
double knic = 5.0;
boolean gostpec = false;

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

!(0 >= 2) != olbri == ((4 == 2) && !(lal >= hodspos) == haph < 3 != buintscod == 9 <= 9) || knic == 6 || gostpec

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?

Related puzzles:

• While loops and for loops: Correct Solution (1fi8-mh00-9k76-yqh)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d90-esq3-miok-bjbz-2)