I played around with this a bit more and arrived at something much faster
than my initial approach which is in fact pretty slow.
Raul :
6!:2 'daten28601 5e6 $ 20180102'
1.40457
My first take :
6!:2 ' ff("0) 5e6 $ 20180102'
87.6379
My second take:
6!:2 'fff("0) 5e6 $ 20181122'
5.19095
ff =: 3 : '''-'' 4 7 } 1 1 1 1 2 1 2 1": 10#.inv y'
fff =: 3 : '''0123456789-''{~0 0 0 0 10 0 0 10 0 0+10 10 10 10 1 10 10
1 10 10#: y'
A variant on Raul's method is to use expand rather than copy
(expand is slower though).
b&#^:_1 where b is a boolean list is *Expand* (whose fill atom f can be
specified by *fit*, b&#^:_1!.f or #^:_1!.f )
]DYP=: -. (i.10)e.4 7
1 1 1 1 0 1 1 0 1 1
daten28602=: DYP #^:_1!.'-'"1 ":@,.
On Wed, Apr 4, 2018 at 7:08 PM, Joe Bogner <joebog...@gmail.com> wrote:
> Raul, that is great. I have used # thousands of times probably but
> never encountered this use
>
> "The complex left argument a j. b copies a items followed by b fills.
> The fit conjunction provides specified fills, as in #!.f ."
>
> http://www.jsoftware.com/help/dictionary/d400.htm
>
>
> I'm glad I asked because something simple like this uncovers new ways
> of thinking
>
> Jimmy - Same goes for yours too. Raul's approach is much speedier
> however yours highlighted an interesting technique for the future.
>
> Thank you both
>
> On Wed, Apr 4, 2018 at 6:18 PM, Jimmy Gauvin <jimmy.gau...@gmail.com>
> wrote:
> > This might be fast :
> >
> > '-' 4 7 } 1 1 1 1 2 1 2 1 ": 10#.inv 20170209
> >
> > 2017-02-09
> >
> >
> > On Wed, Apr 4, 2018 at 6:04 PM, Raul Miller <rauldmil...@gmail.com>
> wrote:
> >
> >> Here's one approach:
> >>
> >>
>
> DXP=: (8#1) j. (i.8)e.3 5
> >>
>
> daten28601=: DXP #!.'-'"1 ":@,.
> >>
> >>
>
> 6!:2 'daten28601 (5e6 1 $ 20180102)'
> >> 0.659381
> >>
> >> --
> >> Raul
> >>
> >> On Wed, Apr 4, 2018 at 5:56 PM, Joe Bogner <joebog...@gmail.com> wrote:
> >> > I'm curious if there is a speedier way to convert a date stored as a
> >> > number like 20180101 or 20170228 to the ISO 8601 equivalent:
> >> >
> >> > This does OK
> >> >
> >> > datenumToISO =: 3 : 0
> >> > (4&{. , '-' , 2&{.@(4&}.) , '-' , _2&{.)"1 ": y
> >> > )
> >> >
> >> > datenumToISO 20180101
> >> > 2018-01-01
> >> > datenumToISO 20180228
> >> > 2018-02-28
> >> >
> >> >
> >> > But is slower than I'd like ... no big deal but just curious
> >> >
> >> > 6!:2 'datenumToISO (5e6 1 $ 20180102)'
> >> > 4.29083
> >> >
> >> > sprintf is slow
> >> >
> >> > dateNumToISO2 =: 3 : 0
> >> > '%d-%02d-%02d' sprintf ,:(0 100 100 #: y)
> >> > )
> >> >
> >> > (6!:2) 'dateNumToISO2 (1e5 # 20180102)'
> >> > 2.34002
> >> > (6!:2) 'dateNumToISO2 (1e6 # 20180102)'
> >> > 25.4977
> >> >
> >> >
> >> > 8!:2 shows promise but I can't figure out the formatting string to add
> >> > a leading zero if it's possible
> >> >
> >> > (6!:2) '8!:2 (0 100 100 #: (5e6 # 20180102))'
> >> > 1.4853
> >> >
> >> > 'q<->,q<->,d' 8!:2 (0 100 100 #: (1 # 20180102))
> >> > 2018-1-2
> >> > ------------------------------------------------------------
> ----------
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