Louis:
> How do I sort the following lines by
> the numbers only (not by the letters and not by the length).
Hope this helps.....
Let me first simplify the data to make the code snippets easier to follow:
data: [
"1 first of the ones"
"1 last of the ones"
"3 top three"
"3 middle three"
"3 bottom three"
"2 start of the twos"
"2 middle of the twos"
"2 last of the twos"
]
You want a *stable* sort on the first field. End result (on my data) should
be:
sorted-data: [
"1 first of the ones"
"1 last of the ones"
"2 start of the twos"
"2 middle of the twos"
"2 last of the twos"
"3 top three"
"3 middle three"
"3 bottom three"
]
A straight sort will compare the whole line length. So
sort sorted-data: copy data
doesn't preserve the input sequencing for fields with an equal key.
If Rebol's sort were "stable" -- i.e. it kept equal keys in their
original sequence, then all you'd need to do is to write your own
sort compare routine to compare partial keys.
This is the basic code:
sort/compare sorted-data: copy data func [a b] [return a < b]
a and b (you can use any names) are the pairs of records to be compared.
But the code above adds no value to the basic sort, as we want to
sort on the first character of each record (on my data). So:
sort/compare sorted-data copy data func [a b] [
return (copy/part a 1) < (copy/part b 1)]
It's not *quite* what *you* want, as you need to sort on the
first space-deliminated field. One way is to use 'parse:
sort/compare sorted-data copy data func [a b] [
return (first parse a " ") > (first parse b " ")
]
But this doesn't preserve the input sequence -- it looks to me like
Rebol's sort is ***not*** stable. So we need to add the input sequence
to each key as part of the compare. Like this:
sort/compare sorted-data: copy data func [a b /local a-key b-key ] [
a-key: join first parse/all a " " ["-" index? find data a]
b-key: join first parse/all b " " ["-" index? find data b]
;;; print [a-key " " b-key] ;;-- decomment this to see what's
happening
return a-key < b-key
]
This is now a stable sort on my data.
It's not quite what you want because your data starts with a space.
So you need the **second** field in the parse:
sort/compare sorted-data: copy data func [a b /local a-key b-key ] [
a-key: join second parse/all a " " ["-" index? find data a]
b-key: join second parse/all b " " ["-" index? find data b]
print [a-key " " b-key] ;;-- decomment this to see what's
happening
return a-key < b-key
]
It should now work on your data, as long
as all your integers remain all as three digits.
If you start to use unequal length
integers, you'll need to normalise them in the sort key.
For your data, I get (I'm assuming you have it in a block as a
string-per-line):
print mold data
[
" 454 en tw"
" 395 en th"
" 313 kai o"
" 175 oi de"
" 314 eij thn"
" 174 eij ton"
" 124 kai ouk"
" 123 kai thn"
" 219 ek tou"
" 160 kai en"
" 142 kai to"
" 126 tw qew"
" 166 kai h"
" 096 ei de"
" 094 ou mh"
" 091 ei mh"
" 120 thj ghj"
" 120 en toij"
" 112 estin o"
" 108 en taij"
" 118 o kurioj"
" 096 proj ton"
" 088 kai touj"
" 082 kai idou"
" 115 kai ta"
" 111 o uioj"
" 111 de kai"
" 103 ek twn"
" 114 eipen autoij"
" 104 tou anqrwpou"
" 071 legei autoij"
" 063 twn ioudaiwn"
" 105 proj auton"
" 092 oi maqhtai"
" 082 legei autw"
" 078 eipen autw"
" 103 ek thj"
" 090 ina mh"
" 086 autw o"
" 084 ou gar"
" 101 apo tou"
]
>> print mold sorted-data
[
"063 twn ioudaiwn"
"071 legei autoij"
"078 eipen autw"
"082 kai idou"
"082 legei autw"
"084 ou gar"
"086 autw o"
"088 kai touj"
"090 ina mh"
"091 ei mh"
"092 oi maqhtai"
"094 ou mh"
"096 ei de"
"096 proj ton"
"101 apo tou"
"103 ek twn"
"103 ek thj"
"104 tou anqrwpou"
"105 proj auton"
"108 en taij"
"111 o uioj"
"111 de kai"
"112 estin o"
"114 eipen autoij"
"115 kai ta"
"118 o kurioj"
"120 thj ghj"
"120 en toij"
"123 kai thn"
"124 kai ouk"
"126 tw qew"
"142 kai to"
"160 kai en"
"166 kai h"
"174 eij ton"
"175 oi de"
"219 ek tou"
"313 kai o"
"314 eij thn"
"395 en th"
"454 en tw"]
Some of the lines it makes a difference on are the 111s and the 120s --
they would be swapped with a simple sort, or randomised within themselves by
a non-stable one.
Hope that makes sense,
Sunanda.
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