On 15-May-02, G. Scott Jones wrote:
> From: "Volker Nitsch"
> ...
>> not sure if this helps, but since i spended some time to it,
>> i post ;)
> <snipped code>
> Hi, Volker,
> Neat idea. Kind of like a good cut of beef, I'm going to have to
> chew on it a bit to fully understand its potential. Thanks for the
> trans-atlantic volley ball pass.
Glad you could work it out, as I couldn't make head nor tail of it. (:
Anyway, I've played around with my idea for sorting according to a
pattern, and while I'm not sure if the following code's very fast (or
bug-free:), like Volker, I post.
There's two functions: One to take a pattern for creating a rule from
and another to use the rule to sort strings or blocks of strings
with. First, the functions...
pattern-rule: func [
"Create a rule for use by pattern-sort."
pattern [string! block!] "An ordered pattern."
/local rule n
][
rule: copy []
n: 1
forall pattern [
append rule reduce [pattern/1 to-paren reduce ['r n] '|]
n: n + 1
]
append rule reduce ['skip to-paren reduce ['r n]]
reduce ['some rule]
]
pattern-sort: func [
{Sort a string or block of strings based on a rule created
by pattern-rule.}
series [string! block!] "Series to sort."
rule [block!] "Pattern rule."
/reverse "Reverse sort order."
/local ptrs blk r pos val
][
ptrs: copy []
blk: copy []
r: func [n][append/only blk n]
bind rule 'r
either string? series [
parse/case series rule
pos: 1
foreach n blk [
append/only ptrs reduce [
n pick rule/2 (n - 1) * 3 + 1
]
val: next first back tail ptrs
if 'skip = val/1 [change val pick series pos]
pos: pos + either char? val/1 [1][length? val/1]
]
][
forall series [
clear blk
parse/case series/1 rule
append/only ptrs copy blk
append last ptrs series/1
]
]
either reverse [sort/reverse ptrs][sort ptrs]
clear series
forall ptrs [append series last ptrs/1]
series
]
And some examples of use...
>> rule-1: pattern-rule "aAbBcC"
== [some [#"a" (r 1) | #"A" (r 2) | #"b" (r 3) | #"B" (r 4) | #"c" (r
5) | #"C" (r 6) | skip (r 7)]]
>> pattern-sort "AacCBb" rule-1
== "aAbBcC"
>> pattern-sort ["Abc" "abc" "aBC" "ABC"] rule-1
== ["abc" "aBC" "Abc" "ABC"]
>> pattern-sort/reverse ["Abc" "abc" "aBC" "ABC"] rule-1
== ["ABC" "Abc" "aBC" "abc"]
>> rule-2: pattern-rule "AaBbCc"
== [some [#"A" (r 1) | #"a" (r 2) | #"B" (r 3) | #"b" (r 4) | #"C" (r
5) | #"c" (r 6) | skip (r 7)]]
>> pattern-sort "AacCBb" rule-2
== "AaBbCc"
>> pattern-sort ["Abc" "abc" "aBC" "ABC"] rule-2
== ["ABC" "Abc" "aBC" "abc"]
>> rule-3: pattern-rule ["a" "A" "b" "B" "ch" "c" "C"]
== [some ["a" (r 1) | "A" (r 2) | "b" (r 3) | "B" (r 4) | "ch" (r 5) |
"c" (r 6) | "C" (r 7) | skip (r 8)]]
>> pattern-sort "abcABCchCbA" rule-3
== "aAAbbBchcCC"
>> pattern-sort ["AabA" "chab" "chAB" "cchc" "achA"] rule-3
== ["achA" "AabA" "chab" "chAB" "cchc"]
It seems to work and might be of some use, but I'd test it well before
trusting it. It's had no real-world tests at all...
--
Carl Read
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