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 arce = 4;
double sousan = 5.0;
double ciout = 2.0;
double pren = 5.0;
int dul = 1;
double i = 4.0;

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

arce / 8 % (sousan + ciout - pren * dul + i - 6 % 5) + 8

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 whes = 4.0;
boolean el = false;
int wentwa = 7;
double aqiss = 5.0;
double de = 4.0;
double hespran = 4.0;
double ece = 1.0;
int is = 3;

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

whes != 9 || el == 5 >= 1 == (wentwa != 2) == 3 <= aqiss == de < 8 != 1 <= hespran == ece <= is || 7 >= 1

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 + 8 + "9" + "10"

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 (gf1w-fpy7-0vfo-n3pg)
• Static and runtime types: Correct Solution (wtpa-76st-jwx6-ix5c)
• Variable scope and lifetime: Correct Solution (gevx-w77t-2rcz-09ti)
• Class declarations and object modeling: Correct Solution (17u1-zmm4-vxs8-jd4k-5)