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

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
> _______________________________________________
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> [email protected]
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>
>
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