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 il = 9;
int es = 3;

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

8 - il - (1 % 2 * 3 - 4 - es)

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 mecpra = false;
boolean conuss = false;
boolean eudmial = false;
boolean tonea = false;

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

mecpra || conuss && eudmial != tonea || 4 != 9 && 4 >= 8

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:

• Drawing ASTs for expressions: Correct Solution (b1em-um38-b6ns-z57x)
• Class relationships: Correct Solution (rgmo-1ipi-mb2c-0tee)
• While loops and for loops: Correct Solution (2u8m-8xd4-eryg-t18)
• Static and runtime types: Correct Solution (wtei-owrw-odcr-z8ny)