Steve Graham wrote:
Steve,
Thanks for the feedback. You were right: I did need the permutations.
2 questions:
1) What does the '1+:' accomplish in
else s[j := 1 to *s] || permute(s[1+:j-1]||s[j+1:0], i-1)
2) What does the '--' accomplish in
else (c := !s) || permute(s--c, i-1)
Hi Steve,
(1) the '+:' string subscript syntax is a measure of distance
instead of absolute position. i:j is everything from
position i to position j, while i+:j is the next j characters
beginning at position i. in this case, it's probably not needed,
it's just what I first thought of.
(2) the '--' is cset minus s--c is the cset s with the characters
in cset c (in this case a single character) removed. So it's used
here to remove the single character used on the left of the
concatenation from consideration in the recursive call building
up the right. (That's logically the same operation that the
s[i+:j-1] || s[j+1:0] is doing in the earlier version.)
Hope that helps!
-Steve
--
Steve Wampler [EMAIL PROTECTED]
The gods that smiled upon your birth are laughing now. -- fortune cookie
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