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 vae = 3.0;
double an = 5.0;
int od = 2;

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

vae * an * 2 + od

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 a = 8;
boolean parmo = false;

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

a <= 9 || 4 != 5 && parmo

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:

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• Static and runtime types: Correct Solution (wti4-7uwh-wm68-6bi9)
• While loops and for loops: Correct Solution (y3qh-icjv-s82d-yj)