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 rast = 3.0;
int ecir = 4;

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

rast * ecir - 6 % 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 ceergi = 4.0;
boolean fopod = false;
int troulpess = 4;

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

ceergi > 9 && fopod && troulpess == 3

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"

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 (1end-ujaw-tcd2-qzn)
• Static and runtime types: Correct Solution (wtwv-a1a6-mcg1-m58a)