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 spessbu = 3;

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

2 - (5 - 4 + spessbu) + 3

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:

boolean urpec = true;
int tred = 7;
double pi = 5.0;
double coa = 5.0;

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

!(6 > 5) && urpec && tred != pi && 7 < coa

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 (wtw2-h0cx-wks7-oq3i)
• Booleans and conditionals: Correct Solution (5k15-oogi-5urh-a2i8)
• While loops and for loops: Correct Solution (15v3-8kr8-s5ut-8av)
• Drawing ASTs for expressions: Correct Solution (b05s-b7jb-ucgh-p0o0)