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 re = 7;
double asend = 4.0;
double rigac = 5.0;
double couss = 4.0;
int croubi = 5;

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

3 + 3 * re / 1 + asend - rigac + couss - 8 / croubi

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 stricmor = 1.0;
double suptu = 1.0;
int sopoe = 9;
double oc = 1.0;
double pson = 1.0;
boolean hissphea = false;
boolean ipo = false;

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

stricmor > suptu && sopoe < oc || !(5 > pson) != !hissphea || ipo && 3 <= 1 && !(9 < 4) == 4 >= 0

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

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:

• Closures and event handling: Correct Solution (Lxyt-04ne-rbd2-a6jk)
• Booleans and conditionals: Correct Solution (5hpe-k3v4-Loqx-xo6p)
• While loops and for loops: Correct Solution (2zfp-urps-rkxj-yof)