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 mipok = 9;
int ecsus = 9;

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

2 / (7 - 8 / mipok / 5 * ecsus)

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:

double russbin = 5.0;
double se = 2.0;
int ir = 6;
double ji = 2.0;
int gustdas = 2;

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

(russbin == 5 || se <= ir && 8 < 8) || 6 >= ji || 2 < gustdas

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?

Related puzzles:

• Booleans and conditionals: Correct Solution (5k4h-i7hw-hoa4-2ebg)
• Static and runtime types: Correct Solution (wtez-vwq6-z6i4-ghj5)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1day-xidi-zi46-bpw9-6)
• Booleans and conditionals: Correct Solution (5m7b-txac-utks-xrh4)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d9i-40d2-ag1k-av5p-p)
• Class declarations and object modeling: Correct Solution (17up-fyc7-pen1-qvqq-k)
• Static and runtime types: Correct Solution (wt92-256f-dcfu-xdmp)
• Closures and event handling: Correct Solution (Lzcn-h3vo-nhfj-jk8c)
• While loops and for loops: Correct Solution (33mj-zguy-1yv0-237)
• Closures and event handling: Correct Solution (Ly2a-n31e-gqjz-p7ia)
• Class declarations and object modeling: Correct Solution (17um-412t-i9zq-0rxv-m)
• Static and runtime types: Correct Solution (wt6y-bsjm-texn-2qap)
• Class declarations and object modeling: Correct Solution (17x3-q0tL-inzy-01fv-2)