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 tirbu = 4;
int sche = 1;
int eul = 9;
int acmin = 3;

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

tirbu + sche + 5 - eul / acmin

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 nonan = false;
double rala = 3.0;
boolean a = true;
double po = 4.0;
int westong = 8;

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

nonan && rala < 7 || a && po < westong

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

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 (wtso-9e3x-dwyr-vs4c)
• Variable scope and lifetime: Correct Solution (geyr-xpqt-mrpf-oky2)