Hi, Hallvard,
To ensure "unsorted", first sort, then interleave second and first
halves. (Assuming you have enough distinct values that moving
halfway through the sorted order gives you a different value.)
Hallvard Ystad wrote:
>
> I have a block with, say 10 blocks inside it. Each block has many
> different data types within it (but only one element matters).
> I want to unsort them so that _part of_ the fourth element (a
> string) is not identical in adjacent blocks...
>
> example: [[4 1 7 "nicsrg" 5 6 3 8 2 9] [3 1 2 "sicrtg" 9 8 4 7 6 5]
> [9 3 7 "iscgtn" 6 2 8 5 4 1] [1 3 8 "inctrg" 5 2 9 4 6 7]
> [9 6 5 "ngsirt" 8 2 1 3 7 4] [3 7 8 "igtnrs" 4 1 2 9 5 6]
> [6 4 8 "gnrsit" 2 3 9 1 5 7] [9 5 4 "sntgir" 6 7 8 2 1 3]
> [6 7 4 "gstinr" 1 5 2 3 9 8] [7 9 2 "sgcnit" 5 1 8 3 6 4]]
>
> In the first four blocks, the third character in the fourth element
> is #"c". I want these four blocks split apart. Getting at the
> character in question is easy (foreach b example [print pick fourth
> b 3]), but unsorting the blocks from there?
>
Let's define (and demonstrate) the interleaving function first:
riffle: func [b [block!] /local n j result] [
j: to-integer (n: length? b) / 2
result: make block! n
for i 1 j 1 [
append/only result pick b i + j
append/only result pick b i
]
if odd? n [append/only result last b]
result
]
Which behaves as:
>> riffle [0 1 2 3 4 5 6 7 8 9]
== [5 0 6 1 7 2 8 3 9 4]
>> riffle [0 1 2 3 4 5 6 7 8]
== [4 0 5 1 6 2 7 3 8]
So that (for a trivial case, which I know is already sorted)
>> riffle sort [0 0 0 1 1 1 2 2 2 3 3 3]
== [2 0 2 0 2 0 3 1 3 1 3 1]
adjacent elements are now different. Finally, for your example:
example: [[4 1 7 "nicsrg" 5 6 3 8 2 9] [3 1 2 "sicrtg" 9 8 4 7 6 5]
[9 3 7 "iscgtn" 6 2 8 5 4 1] [1 3 8 "inctrg" 5 2 9 4 6 7]
[9 6 5 "ngsirt" 8 2 1 3 7 4] [3 7 8 "igtnrs" 4 1 2 9 5 6]
[6 4 8 "gnrsit" 2 3 9 1 5 7] [9 5 4 "sntgir" 6 7 8 2 1 3]
[6 7 4 "gstinr" 1 5 2 3 9 8] [7 9 2 "sgcnit" 5 1 8 3 6 4]]
example: riffle sort/compare example func [a b][a/4/3 < b/4/3]
foreach item example [print mold item]
which gives:
[6 4 8 "gnrsit" 2 3 9 1 5 7]
[1 3 8 "inctrg" 5 2 9 4 6 7]
[9 6 5 "ngsirt" 8 2 1 3 7 4]
[3 1 2 "sicrtg" 9 8 4 7 6 5]
[3 7 8 "igtnrs" 4 1 2 9 5 6]
[4 1 7 "nicsrg" 5 6 3 8 2 9]
[6 7 4 "gstinr" 1 5 2 3 9 8]
[7 9 2 "sgcnit" 5 1 8 3 6 4]
[9 5 4 "sntgir" 6 7 8 2 1 3]
[9 3 7 "iscgtn" 6 2 8 5 4 1]
where adjacent (sub-)blocks differ in the third character of the
fourth element.
-jn-
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