http://www.jsoftware.com/help/dictionary/d331.htm says:
"x u;.0 y applies u to a rectangle or cuboid of y with one vertex at the
point in y indexed by v=:0{x , and with the opposite vertex determined as
follows: the dimension is |1{x ..."
But:
|1{,:3 4
|index error
Does this help you understand the nature of Henry's question?
Thanks,
--
Raul
On Thu, Apr 10, 2014 at 11:51 PM, Bo Jacoby <[email protected]> wrote:
>
> f=:(];.0~,:)~
> 3 4 f 'abcdefghijk'
> defg
>
> Note that
>
> ,:3 4
> 3 4
> $,:3 4
> 1 2
>
>
>
> Den 3:01 fredag den 11. april 2014 skrev Henry Rich <[email protected]
> >:
>
> Can anyone explain why
> > (,:3 4) ];.0 'abcdefghijklmnop'
> >defg
> >
> >works?
> >
> >According to Ye Dic, 0{x gives the starting point, and 1{x gives the
> >length. But
> >
> > 0 { (,:3 4)
> >3 4
> > 1 { (,:3 4)
> >|index error
> >
> >AFAICS a table with one row is treated as if it were a table with one
> >column.
> >
> >In any case, to conform to the definition you should use
> >substr =: (];.0~ ,.)~"1 _
> >
> >,. not ,:
> >
> >Henry Rich
> >
> >On 4/10/2014 8:23 PM, Don Guinn wrote:
> >> Yes. I used those for a long time. I think. ;. is faster.
> >> On Apr 10, 2014 6:06 PM, "Raul
> Miller" <[email protected]> wrote:
> >>
> >>> I'm going to be building hashes, but currently it looks like it'll be
> >>> faster to generate them after finding the unique values rather than
> >>> before.
> >>>
> >>> Hashes have great sales pitches in favor of them, but generating them
> >>> takes time.
> >>>
> >>> Meanwhile, getting lots and lots of real memory is relatively cheap.
> >>> According to https://aws.amazon.com/ec2/pricing/ I can use a machine
> >>> with 244 gigabytes of ram for $3.50 an hour. I do not think I'll need
> >>> that much
> memory, even for a short time.
> >>>
> >>> If it helps, though, there's other ways to get a substring:
> >>>
> >>> 4{.3}. 'abcdefghijk'
> >>> defg
> >>> (3+i.4){'abcdefghijk'
> >>> defg
> >>>
> >>> Thanks,
> >>>
> >>> --
> >>> Raul
> >>>
> >>>
> >>> On Thu, Apr 10, 2014 at 6:45 PM, Don Guinn <[email protected]> wrote:
> >>>>
> >>>>
> >>>> Sounds like you can format the data as you want once you get it all.
> >>> Given
> >>>> the amount of data
> there is no way to read it
> >>>> the entire file
> >>>> in an interactive environment. So it has to be indexed or in a
> database.
> >>>> If you really want to use a segmented string you could keep the index
> to
> >>>> the start of each line to
> >>>> quickly get
> >>>> the line. Also, build a hash for the keys you intend to search on
> rather
> >>>> than trying to search the actual file.
> >>>> This index and hash should fit in memory quite easily.
> >>>> When you talk about a file that big, mapped or not, it's still going
> to
> >>>> require the amount of virtual storage the size of the file, which will
> >>> need
> >>>> to be moved from the file or swap into real storage to process.
> >>>> Scanning the entire file
> >>>> will be very slow unless you have lots and lots of real memory.
> >>>>
> >>>> I haven't seen anyone mention an easy way to substring from a text
> file.
> >>> It
> >>>> took me a long time to find it in the dictionary.
> >>>> It really exists.
> >>>> And it was not obvious when I finally did find it. So I will post it
> here
> >>>> for anyone who hasn't found it.
> >>>>
> >>>>
> >>>> substr=:4 : 0 NB. x: start and length, y: string
> >>>>
> >>>> (,:x)];.0 y
> >>>>
> >>>> )
> >>>>
> >>>> 3 4 substr
> 'abcdefghijk'
> >>>>
> >>>> defg
> >>>> ----------------------------------------------------------------------
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> >
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