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 puc = 3.0;
double er = 4.0;
double ba = 4.0;

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

(puc / 5 + er + ba) + 7

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:

int stangni = 7;
int onpeff = 5;
int mo = 8;
double bua = 2.0;
double meouvdesm = 5.0;
int ploser = 7;

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

(stangni < 3 || onpeff >= mo && 1 != bua) || meouvdesm != ploser

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:

• While loops and for loops: Correct Solution (3tth-3xaL-ec1s-qj9)
• While loops and for loops: Correct Solution (w6am-zuse-qosz-pp)