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 nitlad = 1.0;
double om = 3.0;
int ca = 4;

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

2 - nitlad % om / ca * 0 * 3 / 9

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 odia = 8;
int gler = 7;
boolean rorchgol = false;
boolean prawrhed = false;
double e = 2.0;
double hemstrir = 4.0;
boolean pe = true;

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

odia != gler || 9 == 9 && rorchgol || prawrhed && e < hemstrir && pe

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

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:

• While loops and for loops: Correct Solution (3d5y-y72m-ooyv-tLt)
• While loops and for loops: Correct Solution (10ax-t9m0-m8x7-j1z)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1db1-yhx1-xpLz-qewf-0)
• Closures and event handling: Correct Solution (Lz2p-0gd3-850q-mkcs)
• Closures and event handling: Correct Solution (Lvxs-urnj-hc5c-idha)