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:

double im = 3.0;
int li = 9;

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

(im - li) * 6 / 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:

double nism = 2.0;
int lenas = 4;
int hushpras = 6;
int ca = 7;
double blindinth = 5.0;

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

nism < lenas || (hushpras > 8 || ca >= blindinth)

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:

• Booleans and conditionals: Correct Solution (5kes-wvyp-vbfh-i034)
• Class relationships: Correct Solution (rj0x-z4y1-vwue-nnur)
• Class declarations and object modeling: Correct Solution (17vw-02m3-vj4h-owqp-e)
• While loops and for loops: Correct Solution (2rfj-e9qp-8vs3-wi3)
• Class declarations and object modeling: Correct Solution (17w4-aax8-2p7g-udia-c)