[stack] adding construction to factor

I managed to add something like FP's construction form to Factor. It  
treats stacks as if they were vectors in More's array theory, e.g. '5  
== {5}'. I mentioned wanting to do this a few days ago, so I thought  
I'd share. Maybe it's useful.

Here are a few of examples:

    5 [( sq , dup , neg , drop ])  ==  25 { 5 5 } -5 { }
    5 3 2@ [( + , - )]  ==  8 2
    5 [( 5 + , 5 - )]  ==  10 0

And here's the implementation:

: 2@ 2array ;
: 3@ 3array ;
: 4@ 4array ;
: lift dup array? [ 1array ] unless ;
: lower dup length 1 = [ 0 swap nth ] when ;
: construct
   [ lift ] dip
   [ over [ with-datastack ] dip swap lower ] map
   nip [ ] each
;
: )] ;
: [( \ )]
   [ \ , 1array split [ >quotation ] map ] parse-literal
   \ construct suffix
; parsing

- John