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 fa = 3.0;
double seriar = 1.0;

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

7 % (5 + fa - 0 - 4 + seriar)

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:

boolean usssce = true;
double cring = 4.0;
boolean fusia = true;
int tranpad = 2;

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

usssce == (cring <= 2 == 4 < 4 == fusia) && 3 != tranpad

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"

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

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