[aplusdev] Mapped files

[Jon McGrew]

Hi, Alexei.  I would have made the same suggestion that John Mizel
gave to you, in using the "sys.exp" and "sys.imp" functions.  You
are indicating that the solution isn't what you are after, so let
me just make sure that we are all thinking of the same thing.

"sys.exp" (export) and "sys.imp" (import) are utility functions
that can be thought of as being almost a part of the file-write
and file-read facilities.  Because they are separate, however,
you can make sure that you aren't taking any extra overhead for
them in cases where you do *not* need to use them.

Those functions are used for storing and reading nested arrays.
They work by converting your data into a sort of an encoded form,
which is then written out in the form of a flat character vector.
But I want to emphasize that you would not be using that character
vector yourself; your data in your workspace would continue to be
nested data... it is only at the moment that the data is written
to the file that it is converted.

For example:

     mû3 4Ò(1;'Lesha';10;'Mandrake';2;'Sasha';15;'SuSE';3;'Dima';5;'RedHat')

     $load disp     ã get fns for displaying data structure
     disp.disp m    ã "display" the matrix
+4--------------------------+
3+-+ +5----+ +--+ +8-------+|
||1| |Lesha| |10| |Mandrake||
|+i+ +"----+ +i-+ +"-------+|
|+-+ +5----+ +--+ +4---+    |
||2| |Sasha| |15| |SuSE|    |
|+i+ +"----+ +i-+ +"---+    |
|+-+ +4---+  +-+  +6-----+  |
||3| |Dima|  |5|  |RedHat|  |
|+i+ +"---+  +i+  +"-----+  |
+Ì--------------------------+

     disp.BOXû0     ã turn off the display of boxes around data
     
     disp.disp m    ã "display" sample data object in compact form
1 Lesha 10 Mandrake
2 Sasha 15 SuSE    
3 Dima  5  RedHat  
     Òm
 3 4

     ã Writing the data to a file (from variable m):
     `myfile à sys.exp m   ã write data to "myfile.m" dataset

     ã (Next day):
     ã Reading the data back from the file (into variable n):
     nûsys.imp à `myfile   ã read data back in

     disp.disp n
1 Lesha 10 Mandrake
2 Sasha 15 SuSE    
3 Dima  5  RedHat  
     Òn
 3 4

I think the "sys.exp" and "sys.imp" functions are a good solution.
But perhaps I don't completely understand what it is that you need
to do.

--Jon McGrew



Alexei Zalivine wrote:
> 
> Hello John,
> >
> > You can store a nested object by calling sys.exp{}, which encodes it into
> > a character vector.  To convert it back into the nested object use
> > sys.imp{}.
> Oh, this way not very well. Because I want attach a variable and do
> different actions with these data (search, replace, filtering and other).
> After encode it into character vector I loose it. I will work with huge
> amount of data (about handred Mbs per day), and I need the fast and flex
> solution.
> I will lookin for other way to store data.
> >
> > API's for external facilities like databases is usually done using
> > dynamically loaded functions and the system function _dyld{}. See "C
> > Subroutines" under Extensions and Tools in the manual.
> Yes I read about _dyld system function, but I'm bad C programmer. May be
> anybody wrote the cover functions for connect and executing SQL statement
> for such DBs?
> 
> Thank you,
> Alexei.