Re: Skip rows (number of rows?), column type in library(csv)

Hi Wouter,

no, I did not consider creating a pack. These can be just additional
options to csv//2 <http://www.swi-prolog.org/pldoc/doc_for?object=csv/2> and
csv_read_file_row/3<http://www.swi-prolog.org/pldoc/doc_for?object=csv_read_file_row/3>
which
are entirely backward compatible (as far as I can see from the current
documentation and implementation). It seems that creating a pack is only
going to muddy the waters, by adding a layer on top of library(csv) for
something quite trivial and obvious.

Cheers,
Boris


On Tue, Sep 24, 2013 at 2:26 PM, Wouter Beek <[email protected]> wrote:

> Hi Boris,
>
> These options seem indeed quite useful for some use cases involving CSV
> data. I have no opinion as to whether or not they ought to be part of the
> core feature set. Did you consider creating a Pack for them?
> http://www.swi-prolog.org/pack/list
>
> ---
> Cheers,
> Wouter.
>
> E-mail: [email protected]
> WWW: www.wouterbeek.com
> Tel.: 0647674624
>
>
> On Tue, Sep 24, 2013 at 10:05 AM, Boris Vassilev <[email protected]
> > wrote:
>
>> Hello,
>>
>> I am using the (highly useful) library(csv) and I had to do two
>> tricks, in order to:
>> 1. Skip the header;
>> 2. Control (and validate) the datatype of the columns.
>>
>> It is easiest to explain with the code:
>>
>> load_csv.pl
>> ==
>> :- module(load_csv,
>>     [load_csv_file/4
>>     ]).
>>
>> :- use_module(library(csv)).
>>
>> load_csv_file(File, Functor, Skip, ColumnTypes) :-
>>     FirstLine is Skip + 1,
>>     forall(
>>         load_table_row(File, Functor, ColumnTypes, Line, Row),
>>         (   Line >= FirstLine
>>         ->  assertz(Row)
>>         ;   true
>>         )
>>     ).
>>
>> load_table_row(File, Functor, ColumnTypes, Line, Row) :-
>>     csv_read_file_row(
>>         File,
>>         R,
>>         [convert(false),line(Line)]
>>     ),
>>     R =.. [row|RawColumns],
>>     maplist(convert_field, ColumnTypes, RawColumns, Columns),
>>     Row =.. [Functor|Columns].
>>
>> convert_field(atom, Field, Field).
>> convert_field(number, Field, Number) :-
>>     atom_number(Field, Number).
>> % add additional types as needed
>> ==
>>
>> Is there a way to achieve this using the available options that I didn't
>> see?
>>
>> Does anyone thinks it would be useful to add options to the library for
>> A. Skipping N lines at the beginning;
>> B. Loading at most N lines;
>> C. Pass a list of datatypes for validation and convertion of the data
>> fields?
>>
>> In other words, adding options
>> A. 'skip(+Integer)' with a default 0;
>> B. 'nrows(+Integer)' with a default -1 meaning all (or maybe 'infinite'?)
>> C. 'col_types(+List:atom)' which could be for example 'atom',
>> 'number', 'integer', 'float', etc. There is a 'convert(+Boolean)'
>> option at the moment but it only gets in the way if the column has
>> values like "00", "01", ..., "A0", ..., "QZ", etc.
>>
>> If there is any interest and we agree on the interface I can submit a
>> proposed implementation.
>>
>> Cheers,
>> Boris
>> _______________________________________________
>> SWI-Prolog mailing list
>> [email protected]
>> https://lists.iai.uni-bonn.de/mailman/listinfo.cgi/swi-prolog
>>
>>
>
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