Alf 0.9.3 Released

Ruby
1

I’m pleased to announce that alf 0.9.3 has been released and pushed to
rubygems.org!

Alf follows semantic versioning (http://semver.org/) and has not reached
its
first stable 1.0.0 release. Quoting semver.org: “Anything may change at
any
time. The public API should not be considered stable”. Including alf
with
the
version requirement “~> 0.9.0” shouldn’t break your code, though.

This release is a milestone towards 0.10.0 whose aims is to provide new
data-source connectors. Release 0.9.3 contains important bug fixes and a
few
backward compatible features that were already ready for inclusion.

= Alf – Relational Algebra at your fingertips

Alf brings the relational algebra both in Shell and in Ruby. In Shell,
because
manipulating any relation-like data source should be as straightforward
as
a
one-liner. In Ruby, because I’ve never understood why programming
languages
provide data structures like arrays, hashes, sets, trees and graphs but
not
relations… Let’s stop the segregation :wink:

Changes (changelog at
https://raw.github.com/blambeau/alf/master/CHANGELOG.md)

0.9.3 / 2011-07-23

Bug fixes

  • Added Relation#allbut, forgotten in two previous releases
  • Fixed (join xxx, DEE) and (join xxx, DUM)
  • Fixed scoping bug when using attributes named :path, :expr or :block
    in
    Lispy compiled expressions (coming from .alf files)
  • Fixed ‘alf --yaml show suppliers’ that renderer a --text table instead
    of
    a yaml output
  • Fixed bugs when using Date and Time attributes with .rash files
  • Fixed bugs when using Date and Time attributes in restrict expressions
    compiled from the commandline
  • Fixed a few bugs when using attribute names that are ruby keywords
    (restrict & extend)

New operators (available both in shell and in Lispy DSL)

  • Added MATCHING and NOT MATCHING operators. These operators are useful
    shortcuts for the following expressions.

    (matching     l, r) := (project (join l, r), [l's attributes])
(not_matching l, r) := (minus l, (matching l, r))

    For example:

    # Give suppliers who supply at least one part
(matching suppliers, supplies)

# Give suppliers who don't supply any part
(not_matching suppliers, supplies)

  • Added RANK operator, which is useful for for computing quota queries
    as
    illustrated below. See ‘alf help rank’ for details.

    # Give the three heaviest parts
(restrict (rank :parts, [[:weight, :desc]], :pos), lambda{ pos < 3

})

Enhancements when using Alf in shell

  • added ‘alf -r’, that mimics ‘ruby -r’ (require library before run)

  • When alf is invoked in shell (and only in this case), ALF_OPTS is used
    as
    global options to apply as if they were specified inline:

    % export ALF_OPTS="--env=. --yaml"
% alf show suppliers

    is the same as

    % alf --env=. --yaml show suppliers

  • ‘alf --help’ now distinguishes experimental operators (quota in
    particular)
    from those coming from the (much more stable) TUTORIAL D
    specification.
    The
    former should be used with care as their specification may change at
    any
    time.

Enhancements when using Alf in Ruby

  • Alf.lispy now accepts any argument recognized by
    Environment.autodetect;
    it
    obtains its working Environment that way. Among others:

    Alf.lispy(Alf::Environment.folder("path/to/an/existing/folder"))

    is the same as:

    Alf.lispy("path/to/an/existing/folder")

  • Added Relation::DUM and Relation::DEE constants (relations of empty
    heading
    with no and one tuple, respectively). They are also available as DUM
    and
    DEE
    in Lispy functional expressions.

  • Added a Heading abstraction, as a set of attribute (name, type) pairs.

Internal enhancements (extension points)

  • The Reader and Renderer classes accept a Hash of options as third
    constructor argument. These options can be used by extension points.

  • The Environment class now provides a class-based registering mechanism
    ‘ala’
    Reader and Renderer. This allows auto-detecting the target environment
    when
    –env=… is used in shell. See Environment.autodetect and
    Environment#recognizes? for contributing to this extension point.

  • Internals now rely on Myrrha for code generation. This means that all
    datatypes can now be safely used in relations and dumped to .rash
    files in
    particular.