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 strosa = 3;
int ma = 5;

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

strosa * 1 - 5 % ma

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 rirsplo = 2.0;
int likhar = 7;
int cel = 2;
double boght = 1.0;
double faa = 4.0;

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

rirsplo > 5 || (likhar == cel || boght >= faa)

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:

• Variable scope and lifetime: Correct Solution (gf3j-x4xd-p7vc-w24t)
• Class relationships: Correct Solution (rLum-6zgh-6n1L-s1jo)
• Closures and event handling: Correct Solution (Lyan-go5m-gvw0-aov2)