Random sort demonstration

[Geoff Canyon]

On Thu, May 23, 2013 at 1:08 AM, Dar Scott <dsc at swcp.com> wrote:

> The problem is equality in the sort.  It keeps the same order in
> comparison of pairs of items.  For example, the items sorted in the last
> case above as though they were 2,2,3.  The first item is still first.
>
> So...
>
> Use large values for the argument to random() in random sorts.
>


Came here to say this -- in case it's not clear, sorts in LC are stable,
meaning that they don't change the order of the input unless they have to.
This can be useful when you have several different things to sort by.
Suppose you want to sort a list of people by age, and then by name. If the
data looks like

first name,last name,age,other stuff

then you could use:

sort lines of theData by item 1 of each
sort lines of theData by item 2 of each
sort lines of theData numeric by item 3 of each

To Dar's point, here the stable sort means that you should never use this
to get a random sort:

sort lines of someContainer by random(the number of lines of someContainer)

You are almost guaranteed to get less than random results. Instead always
use something like

sort lines of someContainer by random(999999999)

gc