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 scosma = 8;
double neprur = 2.0;
int iclo = 7;

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

scosma - neprur * 7 + iclo - 7 % 5 - 4 * 0 - 7

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 e = 2;
boolean erm = true;
int dio = 9;
double channac = 4.0;
int si = 7;
boolean woish = false;

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

9 == e || erm == (!(dio != 6)) != (3 == 2) != 0 > channac == 3 < si || 4 <= 2 || woish

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:

• While loops and for loops: Correct Solution (wx1q-krwg-5md3-n6)
• Class declarations and object modeling: Correct Solution (17vt-czha-x4be-jrp5-g)