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 craspin = 6;
int sioc = 8;

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

1 - (craspin * sioc - 5)

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 fedfe = 5.0;
int prasmgac = 5;
int hiul = 1;

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

9 < fedfe && 0 <= prasmgac || hiul > 0

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:

• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d9k-veyn-o4Lb-ch6x-g)
• Variable scope and lifetime: Correct Solution (gfbo-qmx7-xn64-L4tk)