World: r3wp

record-sort: func [record [block!] num [integer!]] [
    tmp: copy []
    new: copy []
    foreach [a b c d] record [append/only tmp reduce [a b c d]]
    sort-method: func [a b] [(at a num) < (at b num)]
    foreach rec sort/compare tmp :sort-method [append new rec]
    return new
]


Here is the record-sort example given in the docs.  Problem is this 
only works for records that have four items.

the easier way is forskip. 'foreach needs a binding-trick

build the code then do it :)

Sunanda: Thanks for the example.  I'll play with your example and 
see what I can do.

Volker: Thanks.  I'll take a look at using forskip

why must it be in words?

The goal is to rewrite the record-sort function so that the number 
of elements is not hard coded into the function.

I want to be able to pass the function another value which equals 
the number of elements in a record and then do something like Record: 
array {Elements}

within the function.  This would make the function more universal.

>> print-n: func [record words] [do compose/deep [ foreach [(words)] 
record [print [(words)]]]]

>> print-n [1 2 3 4 5 6 7 8 9] [a b c]
1 2 3
4 5 6
7 8 9

forskip record 4 [append/only tmp copy/part record 4]

Humm.  That looks like it will work.

does sort/skip directly do what you want?

I'm not sure.  I don't think so but I can't remember why not.

Something about reordering the records makes sort/skip not suitable.

(Back to slicing briefly) REBOL already has functionality equivalent 
to slicing as copy-of-subsection, so this would be better represented 
as a very simple mezzanine function that does the work. If you mean 
slicing as reference-to-subsection-in-place, that would be worth 
adding new support for. Something like:

slice!: make object! [start: end: none]

slice: func [[catch] s [series!] /from b [integer!] /to e [integer!] 
/len l [integer!]] [
    b: either from [at :s b] [:s]
    e: case [
        to at :s e
        len skip :b l
        true tail :s
    ]
    if greater? index? :b index? :e [to: :e e: :b b: :to]
    make slice! [start: b end: e]
]

sort/skip --- I get you -- like it's not easy to sort on the 2-digit 
numbers here:
sort/skip [99 10 2       98 11 5        97 12 4] 3
But it is possible with /all and a parameter into the function

Lots to think about and try.  Thanks a bunch guys for your help.

When I get the function rewritten, I will upload it to the library.

Sunanda, do you mean sort on the second field? Try passing an integer 
or block of integers to the compare refinement of sort.

Rather than a comparator function.

I mean the middle of the three fields, sorting a 3-field record:
  sort-func: func [a b] [return a/2 < b/2]

  sort/skip/all/compare [99 10 2       98 11 5        97 12 4] 3 :sort-func
== [99 10 2 98 11 5 97 12 4]

sort/skip/compare data 3 2

The 2 passed to /comapare means the second field.

Clever -- I didn't know that. Thanks. 

But I tend to use the compare function to get stable sorts.  The 
[x < y]  was just  to shorten the example.

(sorry, /compare)

What, sort isn't stable?

I've always found it to be so.

Not unless you return +1 ,0,  -1
Returning true/false is not guaranteed to be stable

Sort hasn't crashed on me if that's what you mean by unstable.

It's not.

Stable is to do with the order in which duplicate keys are returned.

Looks like stable camwe with /core 2.5
http://www.rebol.com/docs/core25.html

Any mathematicians here ?

On this page : http://www.mja.com.au/public/issues/178_03_030203/sim10248_fm.html#CHDBFAJE

There is this formula


Absolute CVD risk can be calculated from the formula: Probability 
of CVD = 1/(1 + e- k ), where k = – 8.65 + 0.057*age – 0.61*sex + 
0.749*antihypertensive medication + 0.008*systolic blood pressure 
+ 0.458*smoking + 0.18*cholesterol – 0.234*HDL cholesterol + 0.857*diabetes.

what does e stand for ?  Is that some type of log calculation ?

The exp function in REBOL?

It's a long time since I did any high school math :(

cvd: divide 1 1 + exp negate (-8.65 + (0.057 * age) - (0.61 * sex) 
+ (0.749 * ahm) + (0.008 * sbp) + (0.458 * smo) + (0.18 * cho) - 
(0.234 * hdl) + (0.857 * dia))

Based on the formula on the page there.

e is a constant - log is base 10 by default, ln (natural log) is 
base e

(ln = log-e in Rebol)

The exp function calculates e raised to the exponent of the argument 
to the function. If you look on the the web page he is referencing, 
you will see that where he puts e -k, the -k is in superscript, indicating 
that it is to be treated as an exponent.

Great. My function gives the same result as yours.

Seems however, that sex is 1 for female, and 0 for male for this 
to work ( being male confers a higher risk ).

Does now/time give military time?

Almost, no leading zero. Try: now/time + 12:00

If I have an object with a function:
o: make object! [f: func [] [print "Hello World!"]]

Is there a shorter/faster way to get the function without evaluating 
it than:
get in o 'f
?

Shorter?
g i o 'f
:)

lol :P