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 peu = 2;
double i = 4.0;

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

peu * (3 / 7 + i)

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 manmi = 5.0;
double obos = 1.0;
double skurspar = 1.0;
int crie = 4;

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

manmi < 3 || 1 != obos || skurspar == crie

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:

• Static and runtime types: Correct Solution (wtnL-jg58-vmzh-h5h8)
• Variable scope and lifetime: Correct Solution (ger4-L093-oywm-c41r)
• Drawing ASTs for expressions: Correct Solution (b2tL-dfq4-m90d-1Lh2)