Hi,

Great book, really enjoying it so far.

On page 118, you describe the small "loop partitioning" optimization that can be used to eliminate the conditional within the loop.

I believe the conditional will always evaluate to true since the expression matches the one in the 'test' component of the for loop that surrounds it (and the value of i is not changed in the body of the for loop).

Looks like the right-hand side of the expression in the if statement needs to be changed to 'in.length() - 1' to have any effect (if the intended effect is to eliminate recursive calls that result in no additional work being done).

Thanks,
-Matt

Yeah you are right, it seems that even if we remove "if" line alltogether the function will still work, it will just have an extra function call where the loop will not be executed.

Actually when working on this problem my first solution was different from the author's:

public void combine(int i)
{
if (i == in.length())
System.out.println(out);
else {
combine(i + 1);
out.append(in.charAt(i));
combine(i + 1);
out.setLength(out.length() - 1);
}
}

In this case the function combine(i) should print all combinations in the substring (i, in.length()).

From the example "wxyz" the set of all combinations of "wxyz" is the set of all combinations of "xyz" plus the same set where each combinations is prepended with "w".

The only difference is that the function above will also print empty string as one of the outputs (i was thinking in terms of power sets and power set includes empty set as one of its elements).