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 he = 4;
double ma = 2.0;
int ciss = 2;
double te = 1.0;
double lianra = 4.0;

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

6 % (he % ma - ciss % 3) + te - lianra

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 isstro = 6;
int ic = 1;
double sa = 5.0;
boolean ucma = true;
double frirm = 1.0;
double ethart = 2.0;

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

!(isstro < 8) && 0 >= 4 || ic > sa || ucma && 0 == 4 || frirm == ethart

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:

• While loops and for loops: Correct Solution (3cdk-hLoa-dxLz-exw)
• Static and runtime types: Correct Solution (wtg0-a19L-L2n5-0ztd)