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 ca = 3.0;
double ejo = 1.0;
double tiac = 5.0;
double prodon = 4.0;
int qos = 3;
int cac = 3;

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

ca * ejo * 9 - tiac * prodon - qos * 4 - cac

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 stalm = 4;
int weha = 1;
double cea = 3.0;
int vomin = 3;
int io = 6;
boolean miariath = true;

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

2 <= 4 && 5 >= 1 && !(stalm >= 4) || (weha < cea != !(vomin > 0) == 4 < io) == miariath

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" + 7) + 8

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 (wtxf-hzbp-zgag-qqit)
• Static and runtime types: Correct Solution (wt7s-m66a-6oxw-kcoL)