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 ra = 7;
double gios = 4.0;
int decthed = 7;

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

ra * 5 + 9 / gios / decthed % 9

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 iss = 1.0;
double hecmim = 1.0;
int pec = 2;
boolean archaen = false;
boolean gatrop = false;

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

iss > 0 != hecmim >= pec != archaen && 4 < 5 == gatrop

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"

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 (gexy-84mi-1r70-8zfr)
• Static and runtime types: Correct Solution (wtsa-5d18-smdp-nmuj)