[SEJeff]

Yeah kdb is built so that the entire core of the db fits in L1 CPU cache. It really is an impressive feat of engineering and optimization.

I did hate it when we used it however. It required more or less a team of people doing querying on it fulltime. Have you seen the queries in Q? It looks like someone set the baud speed wrong on a serial connection:

From wikipedia's page on Q (the query language of kdb):

    The factorial function can be implemented directly in Q as
    
    {prd 1+til x}
    or recursively as
    
    {$[x=0;1;x*.z.s[x-1]]}

[PeCaN]

Makes sense to me, assuming 'til' is 'iota' and 'prd' is 'fold-with-multiplication'.

I don't know Q, but I'd guess you read it right-to-left like J/K/APL. `x` is the right argument (in J it's `y`), so if we were to call `factorial 5`:

1. Create an array of [0,x) | 0, 1, 2, 3, 4

2. Add 1 to each element of the array | 1, 2, 3, 4, 5

3. Fold the array with multiplication | 120

Array languages are super elegant and fun once you use them a bit.

[icen]

It's not like that first factorial function is actually any worse than the usual Haskell one:

    fac = \n -> product [1..n]

The recursive one is also much the same as a Haskell one, but Q is hardly built around idiomatic recursion.