Functional selectors in Cupt
Eugene V. Lyubimkin
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%man% = NAME =
%man%
%man% cupt_functionselectors - syntax of functional selectors in cupt package manager
%man%

= AIM =

Functional selectors are used for fine-grained selection of versions. While
standard mechanisms provide a way to select versions by package name, version
string and/or distribution, functional selectors embed a microlanguage to
select versions by their various properties.

= SYNTAX =

Functional selector expression (FSE) consists of **function name** and **list of arguments**:

'//function_name//``(``//argument1//, //argument2//, ... //argumentN//``)``'

Every argument can be a FSE itself or a string. Arguments are separated by the
comma (``,``).  Additional whitespace characters (space, tab, newline) are
allowed (and ignored by parser) anywhere except between the function name and
the opening bracket.

If the argument is a string and contains commas or round brackets, the argument
should be quoted by placing the ``/`` character around it
('``/``//argument//``/``').

If the function receives no arguments, arguments bracked may be omitted:
'//function_name//' is an equivalent to '//function_name//``()``'.

The expression '//argument1// ``&`` //argument2// ``&`` ... ``&``
//argumentN//' is a special short form for '``and(``//argument1//,
//argument2//, ...
//argumentN//``)``'. Similarly, the expression '//argument1// ``|``
//argument2// ``|`` ... ``|`` //argumentN//'
is a special short form for '``or(``//argument1//, //argument2//, ...
//argumentN//``)``'

= FUNCTION REFERENCE =

== Logic functions ==

Receive FSEs as arguments.

|| Function name and arguments | Argument count | Returns versions which... |
| ``and(``//fse1//, //fse2//, ... //fseN//``)`` | ≥ 1 | satisfy all of the //fse1//..//fseN// |
| ``or(``//fse1//, //fse2//, ... //fseN//``)`` | ≥ 1 | satisfy any of the //fse1//..//fseN// |
| ``not(``//fse//``)`` | 1 | don't satisfy //fse// |
| ``xor(``//fse1//, //fse2//``)`` | 2 | satisfy either //fse1// or //fse2// but not both |

== Package property functions ==

|| Function name and arguments | Short alias | Returns versions which... | Notes |
| ``package:name(``//regex//``)`` | ``Pn`` | package name matches //regex// |
| ``package:installed()`` | ``Pi`` | belong to to installed packages | applies only to binary versions |
| ``package:automatically-installed()`` | ``Pai`` | belong to automatically installed packages | applies only to binary versions |

== Common version property functions ==

Apply to source and binary versions.

|| Function name and arguments | Short alias | Returns versions which... |
| %regex_syntax(version)% | ``v`` | version string matches //regex// |
| %regex_syntax(maintainer)% | ``m`` | maintainer matches //regex// |
| %regex_syntax(priority)% | ``p`` | priority matches //regex// |
| %regex_syntax(section)% | ``s`` | section matches //regex// |
| ``trusted()`` | ``t`` | come from at least one release with a valid cryptographic signature |
| ``field(``//field_name//, //regex//``)`` | ``f`` | value¹ of the non-standard (not recognized by Cupt) field //field_name// matches //regex// | 

¹If the version does not contain a field //field_name//, its value is assumed being empty string; and it can still match if regular expression matches empty string.

=== release-related functions ===

Functions from this family receive one string argument (//regex//) and return
versions which come from at least one release where //property// (see the
following table) matches the regular expression //regex//.

|| Function name | Short alias | //Property// |
| ``release:archive`` | ``Ra`` | archive |
| ``release:codename`` | ``Rn`` | codename |
| ``release:component`` | ``Rc`` | component |
| ``release:version`` | ``Rv`` | version |
| ``release:vendor`` | ``Ro`` | vendor |
| ``release:origin`` | ``Ru`` | origin (base URI) |

== Binary version property functions ==

Apply only to binary versions.

|| Function name and arguments | Short alias | Returns versions which... |
| %regex_syntax(source-package)% | ``sp`` | source package matches //regex// |
| %regex_syntax(source-version)% | ``sv`` | source version string matches //regex// |
| ``essential()`` | ``e`` | have 'Essential' flag set |
| ``installed()`` | ``i`` | are installed in the system |
| %regex_syntax(description)% | ``d`` | description matches //regex// |
| %regex_syntax(provides)% | ``o`` | provides at least one virtual package which matches //regex// |

== Source version property functions ==

Apply only to source versions.

|| Function name and arguments | Short alias | Returns versions which... |
| %regex_syntax(uploaders)% | ``u`` | have at least one uploader which matches //regex// |

== Binary relation functions ==

Apply only to binary versions.

=== forward dependencies ===

Functions from this family receive one FSE-argument (//fse//) and return all versions
which satisfy the dependency of type //relation type// for //fse// (see the following table).

|| Function name | Short alias | //Relation type// |
| ``pre-depends`` | ``Ypd`` | Pre-Depends |
| ``depends`` | ``Yd`` | Depends |
| ``recommends`` | ``Yr`` | Recommends |
| ``suggests`` | ``Ys`` | Suggests |
| ``enhances`` | ``Ye`` | Enhances |
| ``conflicts`` | ``Yc`` | Conflicts |
| ``breaks`` | ``Yb`` | Breaks |
| ``replaces`` | ``Yrp`` | Replaces |

=== reverse dependencies ===

Functions from this family receive one FSE-argument (//fse//) and return all
versions for which at least one version from //fse// satisfies the dependency
of type //relation type// (see the following table).

|| Function name | Short alias | //Relation type// |
| ``reverse-pre-depends`` | ``YRpd`` | Pre-Depends |
| ``reverse-depends`` | ``YRd`` | Depends |
| ``reverse-recommends`` | ``YRr`` | Recommends |
| ``reverse-suggests`` | ``YRs`` | Suggests |
| ``reverse-enhances`` | ``YRe`` | Enhances |
| ``reverse-conflicts`` | ``YRc`` | Conflicts |
| ``reverse-breaks`` | ``YRb`` | Breaks |
| ``reverse-replaces`` | ``YRrp`` | Replaces |

== Source relation functions ==

=== forward dependencies ===

Apply only to source versions and return binary versions.

Functions from this family receive one FSE-argument (//fse//) and return all
versions which satisfy the build-time dependency of type //relation type// for
//fse// (see the following table).

|| Function name | Short alias | //Relation type// |
| ``build-depends`` | ``Zbd`` | Build-Depends |
| ``build-depends-indep`` | ``Zbdi`` | Build-Depends-Indep |
| ``build-conflicts`` | ``Zbc`` | Build-Conflicts |
| ``build-conflicts-indep`` | ``Zbci`` | Build-Conflicts-Indep |

=== reverse dependencies ===

Apply only to binary versions and return source versions.

Functions from this family receive one FSE-argument (//fse//) and return all
versions for which at least one version from //fse// satisfies the
build-dependency of type //relation type// (see the following table).

|| Function name | Short alias | //Relation type// |
| ``reverse-build-depends`` | ``ZRbd`` | Build-Depends |
| ``reverse-build-depends-indep`` | ``ZRbdi`` | Build-Depends-Indep |
| ``reverse-build-conflicts`` | ``ZRbc`` | Build-Conflicts |
| ``reverse-build-conflicts-indep`` | ``ZRbci`` | Build-Conflicts-Indep |

== Metafunctions ==

=== defining functions ===

The function **``with``** defines a user function with no parameters
which can be used as FSE-argument in the subexpression.

Syntax:

``with(``//function_name//, //function_expression//, //subexpression//``)``

|| Argument | Meaning |
| //function_name// | user-defined function name, must start with an underscore (``_``) |
| //function_expression// | FSE, function value |
| //subexpression// | FSE which the defined function can be used in |

This function returns the value of //subexpression//.

=== recursing ===

The function **``recursive``** defines a recursive transformation FSE.

Syntax:

``recursive(``//subresult_function_name//, //initial_subresult//, //iterating_expression//``)``

|| Argument | Meaning |
| //subresult_function_name// | user-defined function name, must start with an underscore (``_``) |
| //initial_subresult// | FSE, initial value of //subresult_function_name// |
| //subexpression// | FSE to compute on each recurse iteration, which //subresult_function_name// to be used in |

The function works as follows:

+ //subresult_function_name// defined as //initial_subresult//
+ the value of //iterating_expression// is computed
+ if this value is equal to //subresult_function_name()// its returned as function result 
+ //subresult_function_name// redefined as ``or(``//subresult_function_name//, //iterating_expression//``)``
+ go to step 2


=== mapping ===

The function **``fmap``** applies many functions to the same expression and combines their results.

The expression

``fmap(``//fse//, //function_name_1//, ..., //function_name_N//``)``

is equivalent to

``or(``//function_name_1//``(``//fse//``)``, ..., //function_name_N//``(``//fse//``))``

== Miscellaneous ==

|| Function name and arguments | Value |
| ``best(``//fse//``)`` | filters out those versions from //fse// for which there are another version of the same package and higher pin |
| ``binary-to-source(``//binary_fse//``)`` | converts binary versions, selected by //binary_fse//, to their corresponding source versions |
