NAME

LINQ - an interpretation of Microsoft's Language Integrated Query

SYNOPSIS

  use feature qw( say );
  use LINQ qw( LINQ )';
  
  my $double_even_numbers =
    LINQ( [ 1 .. 100 ] )
      ->where( sub { $_ % 2 == 0 } )
      ->select( sub { $_ * 2 } );
  
  for my $n ( $double_even_numbers->to_list ) {
    say $n;
  }

DESCRIPTION

LINQ is basically an application of SQL concepts to arrays and iterators. Hopefully this implementation will eventually cover other data types like SQL tables, XML and JSON data, etc.

Not much is documented yet, but the test suite includes numerous examples of LINQ's usage.

FUNCTIONS

The LINQ, Range, and Repeat functions return LINQ collections, objects implementing the LINQ::Collection interface.

LINQ( SOURCE )

Creates a LINQ collection from a source. The source may be an existing LINQ collection, which will be returned as-is, an arrayref of items, or a coderef which will be called in scalar context and expected to return a single item each time it is called. It should return the special value LINQ::END() to indicate that the end of the collection has been reached.

LINQ may be exported, but is not exported by default.

Range( MIN, MAX )

Returns a LINQ collection containing the range of numbers from MIN to MAX. If MIN is undef, it is treated as 0. If MAX is undef, it is treated as positive infinity.

If you want a range from 0 to negative infinity, use:

  my $below_zero = Range( 0, undef )->select( sub { -$_ } );

Range may be exported, but is not exported by default.

Repeat( VALUE, COUNT )

Returns a LINQ collection containing the same value multiple times. If COUNT is undef, then it is treated as infinity.

Repeat may be exported, but is not exported by default.

END()

Returns the special value LINQ::END().

Repeat may be exported, but is not exported by default, and I recommend calling it by its fully qualified name for clarity.

HISTORY

I wrote this back in 2014, but never released it. After a discussion about how nice it would be to have a programming language which used SQL concepts natively, eliminating the need to "map" between how your application handled data and how your database handled data, I remembered this. So I thought I'd push what I had so far onto CPAN and maybe think about reviving it.

BUGS

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=LINQ.

SEE ALSO

LINQ::Collection.

https://en.wikipedia.org/wiki/Language_Integrated_Query

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2014, 2021 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.