[Chicken-users] destructive sort! really destructive

[Loïc Faure-Lacroix]

I’m not sure if it’s how it is supposed to work. I have a list that looks like this:

'((23 14 19) (28 9 19) (10 10 19) (16 14 18)

 (14 8 18) (25 13 18) (13 13 17) (10 7 17) 

 (27 12 17) (21 12 16) (10 6 16) (5 11 16) 

 (25 11 15) (6 5 15) (0 10 15) (3 4 14)

 (5 3 13) (23 2 12) (16 1 11) (29 0 10) 

 (15 8 9) (9 5 9) (4 7 8) (17 6 7) 

 (17 5 6) (28 3 4) (10 0 4) (7 2 3)

 (20 1 2) (11 0 1))

When calling this function on this list let say (define a …)

(sort! a (lambda (x y) (< (car x) (car y))))

Returns the sorted list and then

a is equal to:

((23 14 19) (23 2 12) (25 13 18) (25 11 15) (27 12 17) (28 9 19) (28 3 4) (29 0 10))

I guess that I understand why I get such result. Since the list is sorted destructively, the elements within the list are changed. Except the variable “a” is still pointing to the cons of (23 14 19) . rest. For that reason, I’m missing some elements in my list as I’m not referencing a to the new head. I guess it should be pointed out in the documentation that the behaviour of “sort!” might be quite different from what someone might be expecting… 

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Loïc Faure-Lacroix
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