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 bront = 3;
double cagong = 3.0;
int nilflef = 8;
int sa = 7;
int tefioss = 9;

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

bront * (cagong - nilflef * 0 / 2 + sa - tefioss)

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 preic = 2;
int hira = 9;
int ledso = 2;
int shimix = 2;
boolean atre = false;
boolean mecksqud = false;

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

preic > hira == ((7 != ledso) == shimix > 5 == 8 < 2) || atre == mecksqud

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

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 (5mat-coim-jtcw-qv7s)
• Static and runtime types: Correct Solution (wtux-x8Lm-riqd-6ab0)