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 usshe = 4.0;
int miltpil = 9;
double cherd = 4.0;

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

3 - usshe - miltpil + 6 + (cherd + 5 * 9)

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 prass = true;
double ciscel = 1.0;
int ol = 2;
boolean tonpo = false;

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

0 > 0 || prass != (ciscel == 5) == (!(ol != 7)) && 2 == 5 || tonpo

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:

• Static and runtime types: Correct Solution (wtgn-pw0m-tj5i-f0xb)
• While loops and for loops: Correct Solution (1hbc-rvoj-eb0c-iwo)