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 oc = 1;

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

oc * 2 + 8

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 denpan = 2;
int rerd = 6;

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

3 != denpan || rerd < 3

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"

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:

• Static and runtime types: Correct Solution (wt8e-7Log-ddvs-0fw6)
• Class relationships: Correct Solution (rjek-awg5-4cym-Lnvo)
• Variable scope and lifetime: Correct Solution (gey8-ipb7-trst-mvd9)
• Class relationships: Correct Solution (rk3q-xtt6-gh2x-fa2o)