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 ce = 5;
double mudscli = 2.0;

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

ce + (mudscli - 5 % 2)

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:

double ziphoerd = 4.0;
boolean hi = true;
double spomint = 1.0;
double scriscos = 5.0;

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

9 > ziphoerd || hi || spomint >= scriscos

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

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 (2ofu-gynj-wzxr-8L4)
• Class relationships: Correct Solution (rLq4-8qis-juL9-hfev)
• Variable scope and lifetime: Correct Solution (gev0-rxiu-44p8-b230)