.. _file_include_partition.hpp:

File partition.hpp
==================

|exhale_lsh| :ref:`Parent directory <dir_include>` (``include``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS



Compile-time partitioning of a typelist based on a binary relation. 



.. contents:: Contents
   :local:
   :backlinks: none

Definition (``include/partition.hpp``)
--------------------------------------


.. toctree::
   :maxdepth: 1

   program_listing_file_include_partition.hpp.rst



Detailed Description
--------------------

Splits an ``HTList<Ts...>`` into two lists: those that satisfy a relation ``Rel<Pivot, T>::value`` (the **pass** bucket) and those that don't (the **fail** bucket). Aliases ``filter_by`` and ``reject_if_by`` expose the two buckets directly, and ``partition_by_key`` lets you partition on derived key types (e.g., ``Size<T>``).

**Example**

//GivenRelthatcomparesElemvsPivotbysize(seePredBy/op_taginpredicates.hpp):
usingL=:ref:`exhale_struct_structctql_1_1detail_1_1HTList`;
usingP=:ref:`exhale_struct_structctql_1_1partition__by`;
usingLeft=P::pass;//elementsXwithLessRel::pred<A,X>::value==true
usingRight=P::fail;


``Rel<Pivot, T>`` must define a ``static constexpr bool value``. 






Includes
--------


- ``htlist.hpp`` (:ref:`file_include_htlist.hpp`)

- ``predicates.hpp`` (:ref:`file_include_predicates.hpp`)

- ``type_traits``



Included By
-----------


- :ref:`file_include_sorted.hpp`




Namespaces
----------


- :ref:`namespace_ctql`


Classes
-------


- :ref:`exhale_struct_structctql_1_1partition__by`


Typedefs
--------


- :ref:`exhale_typedef_partition_8hpp_1a707849ebf32a3cf2aa9252430aa8f3ed`

- :ref:`exhale_typedef_partition_8hpp_1a5b67c1b739e6cf726914dfa1b1536fee`

- :ref:`exhale_typedef_partition_8hpp_1a32d0ffacbd052d05b6f8a74c23274a04`