World: r3wp

But yes, good point :)

No I want a default comparison scheme for pairs (even if it is not 
the one I think is the most usefull) . Error bombings are of no use

What about the comparison of euclidean distances of 2 coordinates 
?

Bring it up with Carl for R3, or suggest it in CureCode. This is 
all a little off-topic for this group anyways - we should be in Core.

I'll try sorting ..

You can't use sort !

sort 10x10 11x11

Use SORT/COMPARE if the default sort order doesn't word for your 
pairs.

sort [10x10 11x11]

oh yeah ...

SORT takes a block

sort uses the x coordinate

should have a sort/y :)

sort/compare pairs func [a b] [all [a/2 < b/2]]

uses the Y coord. Use whatever sorting scheme you like.

yeah .... I had sort/reverse

ALL [...] is of course wrong

too early in the morning ... not awake yet

func [a b] [a/2 < b/2] would have been better

Wait, I somewhere have a handy COMPARE function for writing custom 
sort functions ...

Ok, here it is:

compare: func [

    "Returns -1, 0 or 1 if the first value is lesser, equal, greater 
    than the second value."
    a b /else "Return NONE when equal (useful to chain COMPARE)"
][
    case [a < b -1 a > b 1 else [none] true 0]
]

sort/custom some-pairs func [a b] [compare/else a/2 b/2 compare a/1 
a/2]

That would stable sort Y first, then X for a/y = b/y. Just for exemple's 
sake.

I'd suggest that pair1 > pair2 if the sum of its parts are larger 
than pair2

is a pair is greater if it is further from 0x0

as the crow flies along the co-ordinate axis

but that could mean 100x0 = 0x100 :(

or [1x-2  = -2x1] :))

Christian, I am just compairing two pairs :)

: )   Ok, I see! And that's where SORT 10x10 11x11 came from ;-)

Just a simple issue!  .... I have an image and I want to see if I 
need to enlarge it or not to fit into my box

INSIDE? p1 p2

Maybe that's of use?

that I didn't know

I'll try that one

how about 
100x0 = 0x100 => true
but 100x0 == 0x100 => false

And don't overlook OUTSIDE? p1 p2

Are you suggesting a default sort order for pair here?

because

R2>> 100x0 = 0x100
R2== false
R2>> 100x0 == 0x100
R2== false

yes, just a suggestioni

so, this means -100x0 = 100x0 = 0x100

= 0x-100

probably break too much code

I don't think you can come up with a default here. What if your PAIR! 
is talking width x length ? Than camparing would probably be (width1 
* height1) < (width2 * height2). It really depends on what you use 
pairs for ...

CE for your compare    cmp: func [a b][ sign? a - b]

pairs can be used in more ways than any one of us will come up with 
and will have different premises as to what sort means. let it error 
right away so we know we have to be more specific in our code

CE if your compare function returns -1 0 or 1 then the resulting 
sort will be a stable sort.

sign?: func [

    {Returns sign of number as 1, 0, or -1 (to use as multiplier).}
    number [number! money! time!]
][

    either positive? number [1] [either negative? number [-1] [0]]
]

I don't remember exactly, but COMPARE should be a little bit faster 
and has the advantage of being to able to return NONE if desired

If we can't think of all the possibilities, perhaps we can specify 
some default behaviours which we can over ride with custom sorts 
or whatever

I don't need to see an error all the time :)