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![Exporter.pm
package Maths;
use parent 'Exporter';
our @EXPORT = qw/ min max average /;
our @EXPORT_OK = qw/ sin cos tan /;
our %EXPORT_TAGS = (
list => [qw/ min max average /],
trig => [qw/ sin cos tan /],
);
use Maths qw/ :list /;
$minimum = min(@numbers);](https://image.slidesharecdn.com/exporter-modules-141108173358-conversion-gate01/75/CPAN-Exporter-modules-for-Perl-5-4-2048.jpg)
![SEE ALSO 2/2
• Exporter::Renaming – monkey-patches Exporter to
provide a renaming capability
• Export::Lexical, Exporter::Lexical – subs imported into
lexical scope
• Sub::Exporter::Simple – syntactic sugar for basic
exporting with Sub::Exporter (just use Exporter[::Tiny])
• Sub::Import – Sub::Exporter-like semantics, importing
from any module](https://image.slidesharecdn.com/exporter-modules-141108173358-conversion-gate01/75/CPAN-Exporter-modules-for-Perl-5-49-2048.jpg)
CPAN Exporter modules for Perl 5
- 1. More than youever wanted to know about Perl 5's Exporter modules Neil Bowers NEILB [email protected]
- 2. 44+ modules onCPAN!
- 3. Function library modules use Maths qw/ min /; $min = min(@values); package Maths; use parent 'Exporter'; sub min { ... } package Exporter; ... sub import {...} You're writing one of these
- 4. Exporter.pm package Maths; use parent 'Exporter'; our @EXPORT = qw/ min max average /; our @EXPORT_OK = qw/ sin cos tan /; our %EXPORT_TAGS = ( list => [qw/ min max average /], trig => [qw/ sin cos tan /], ); use Maths qw/ :list /; $minimum = min(@numbers);
- 5. My model forfunction libraries • Only functions exported • Don't export variables • No functions exported by default • You have to ask for ask for everything you want • No (unexpected) namespace pollution • Documents where functions in your code come from (but: tags)
- 6.
- 7. What else mightyou want? • Default exports • Exporting variables • Different (better?) notation for specifying what and how to export • Tags • Constants (creating module which define & export them) • Import control • Anonymous subs (on import & export) • Generators (aka currying) • Combined class & function module • Create a mashup module (exporting things from other modules)
- 8. Default exports Specifyingwhat users of your module get when they don't explicitly list anything for import
- 9. Exporter::Auto • Allpublic functions in module exported by default • Doesn't export functions that start with an underscore • Namespace pollution
- 10. Simpler than Exporter.pm When you want more than a completely minimal exporter, but not as much as Exporter
- 11. Exporter::Lite • Alightweight subset of the classic Exporter functionality • Adds the import() function into your namespace • No support for tags, or other features beyond the above
- 12. Exporter::Easy • Basicusage is clean and simple • Has nice way to build up tags ...
- 13. Exporter::Shiny • Simpleinterface for optional exports: • Exporter::Shiny is syntactic sugar around Exporter::Tiny
- 14. Tags Defining namedgroups of the symbols available for import
- 15. Exporter::Easy • Goodif you've got a lot of functions / groups • That's a lot of punctuation though ...
- 16.
- 17.
- 18. Don't export variables! • http://c2.com/cgi/wiki?GlobalVariablesAreBad • http://programmers.stackexchange.com/questions/14810 8/why-is-global-state-so-evil • and • and • and
- 19. Constants Making iteasy to create modules that define and export constants, for example ones that are system-wide
- 20.
- 21. Panda::Export • Function::Exporter+ constants, in XS
- 22. Constant::Exporter • Seealso also supports defining of tags • Const::Exporter – exports immutable variables too (deps++) • Exporter::Constants – support module for Exporter.pm
- 23. Constant::Export::Lazy • Wherethe value of a constant might take a long time to compute, look up in a database, etc
- 24. Import control Moreflexible ways for your module's users to specify which symbols to import, and as what
- 25. Exporter • Theimport list is basically a query, read left to right • You can use a regexp to match what to import • And prefix with ! to negate a clause
- 26.
- 27. Anonymous functions Exportingfrom, and import to, function references
- 28. Exporter::AutoClean • Exportanonymous subs • People can import, but not dip into your namespace
- 29. Exporter::Tiny • Importinto a scalar reference • Doesn't pollute your namespace • For example, if you're making all your public functions exportable
- 30. Alternate notations Otherways to specify what bits of your module to export
- 31. Attribute::Exporter • Attributesused to annotate each function with export rules • Good: export status obvious when you look at each function • Bad: verbose / noisy • See also: Exporter::Simple, Perl6::Export::Attrs
- 32.
- 33. Export::Above • Exportconfig spread through file, but not next to each func
- 34. Exporter::Declare • Declarativesyntax, Moose stylee
- 35. Exporter::Declare • Oryou can put the export status by each sub: • Or you can export an anonymous sub:
- 36. Exporter::Declare - tags • You can define tags up front: • Or specify the tagging with each sub:
- 37. Exporter::Declare • Youcan rename things when you import them: • And a bunch more features. Too many perhaps? • Like Moose/Moo, potential for a lightweight subset?
- 38. Exporter::Declare::Magic • Syntacticsugar for Exporter::Declare • But: depends on 18 CPAN distributions
- 39. Hybrid modules Creatingmodules that can be used either as a class, or as a function library
- 40.
- 41. Making mashup modules Create a module that exports things from multiple other modules
- 42. Exporter::Cluster • Createmodule which export things from other modules
- 43.
- 44. Generators, or currying Fixing arguments to functions at import time
- 45. Sub::Exporter • Basicusage – give list of subs for optional export • Defines a :all/-all tag • You can rename on import • The real power is in export generators though...
- 46.
- 47. Using a Sub::Exportermodule • When importing, you can configure what sub you want • Adds an overhead to all sub calls • I've recently hit a case where this might be the right solution • How many users of the module are using generators...?
- 48. SEE ALSO 1/2 • Badger::Exporter – Exporter + constants + hooks ++ • Sub::Exporter::Progressive – same interface as Sub::Exporter, which is only loaded if advanced features are used, otherwise uses Exporter • Exporter::LexicalVars – create a module that exports lexical variables (!) • Exporter::Proxy – like my Function::Exporter, but exports the whole typeglob and adds exports() for reflection
- 49. SEE ALSO 2/2 • Exporter::Renaming – monkey-patches Exporter to provide a renaming capability • Export::Lexical, Exporter::Lexical – subs imported into lexical scope • Sub::Exporter::Simple – syntactic sugar for basic exporting with Sub::Exporter (just use Exporter[::Tiny]) • Sub::Import – Sub::Exporter-like semantics, importing from any module
- 50.
- 51. Dependencies: the bad& the ugly
- 52.
- 53. Observations • Documentationof exporter modules is often sub-optimal • Particularly for people writing their first exporting module • Very few modules make use of advanced features • Very few modules document their import features • If your module provides advanced import features, you need to let your users know • There's only one exporter module shipped with Perl • There are gaps above and below it
- 54. Conclusion • Exporter::Tinyis a good default for most users • Or Exporter if you don't want the non-core dependency • Exporter::Easy if you've got rich tag needs • Would be nice if Exporter::Tiny supported nested tags • Exporting constants? • Panda::Export for &CONSTANTS • Const::Fast + Exporter::Tiny for immutable variables • Misc others: • Import::Base for mashup modules • Sub::Exporter for generators • Export::AutoClean / Exporter::Tiny for namespace OCD types • Yoda says: • variables export you should not • OO or functions: pick one you should