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 hapsiorm = 6;
double plir = 5.0;

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

4 % 8 * hapsiorm % 1 + plir

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 er = 7;
double esplo = 1.0;
int poucil = 2;

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

(5 > er || !(8 == esplo)) && 8 >= 3 || 0 > poucil

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:

• Booleans and conditionals: Correct Solution (5ipv-uc34-amq0-okzw)
• Variable scope and lifetime: Correct Solution (gf1s-Lk7r-vLo9-8xs9)