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 sinchle = 1.0;
int subre = 5;
double zosal = 4.0;

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

sinchle * (subre + zosal / 9) - 0

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:

int nac = 5;
boolean cherd = false;
double osscan = 2.0;
int es = 9;

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

nac > 0 || (cherd && osscan != es) || 0 != 4

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)

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:

• Static and runtime types: Correct Solution (wtf0-fup2-f9oo-zv7b)
• While loops and for loops: Correct Solution (2d5x-L1pu-hu4L-vys)