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 cisdo = 6;
double anen = 5.0;
double ra = 4.0;
int ipec = 4;

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

5 % cisdo % anen / (5 + ra * ipec) + 1

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 thith = true;
double litchlind = 2.0;
int ensid = 3;
double ced = 2.0;
int rul = 5;

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

!thith == litchlind > 5 && ensid < ced && rul == 6 == 4 < 5 != (!(1 != 8))

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:

• Variable scope and lifetime: Correct Solution (gex4-8xfa-3rdq-jiwp)
• Drawing ASTs for expressions: Correct Solution (b5yp-iii9-eL66-kwj0)
• Static and runtime types: Correct Solution (wtsv-9i5y-Lrvu-wvru)