txt: ## dist_cpan-FRITH-Math-Libgsl-Sort.md
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  # NAME
  
  Math::Libgsl::Sort - An interface to libgsl, the Gnu Scientific Library - Sort.
  
  # SYNOPSIS
  
  ```
  use Math::Libgsl::Raw::Sort :ALL;
  
  use Math::Libgsl::Sort;
  
  ```
  
  # DESCRIPTION
  
  Math::Libgsl::Sort provides an interface to the sort functions of libgsl, the GNU Scientific Library.
  
  This package provides both the low-level interface to the C library (Raw) and a more comfortable interface layer for the Raku programmer.
  
  This package comes with the Sort module tailored to all the real and integer types:
  
  * Math::Libgsl::Sort - default, corresponding to a Math::Libgsl::Sort::Num64
  * Math::Libgsl::Sort::Num32
  * Math::Libgsl::Sort::Int32
  * Math::Libgsl::Sort::UInt32
  * Math::Libgsl::Sort::Int64
  * Math::Libgsl::Sort::UInt64
  * Math::Libgsl::Sort::Int16
  * Math::Libgsl::Sort::UInt16
  * Math::Libgsl::Sort::Int8
  * Math::Libgsl::Sort::UInt8
  
  All the subs of each package have their name prefixed by the relative data type:
  
  Math::Libgsl::Sort has a sub num64sort, while Math::Libgsl::Sort::Int8 has a sub int8sort, and so on.
  
  ### num64sort(:@data, Int :$stride? = 1 --> List)
  
  This sub takes two named arguments: the data array and the stride. The sub returns a List of values: the element of the original array sorted in ascending order.
  
  For example:
  
  ```
  my @data = (10…0)».Num;
  say @data; # output: [10 9 8 7 6 5 4 3 2 1 0]
  my @out = num64sort(:@data, :stride(2)); # sort the elements of @data, with a stride of 2: 10, 8, 6, 4, 2
  say @out;  # output: [0 9 2 7 4 5 6 3 8 1 10]
  
  ```
  
  ### num64sort2(:@data1, Int :$stride1? = 1, :@data2, Int :$stride2? = 1 --> List)
  
  This sub takes four named arguments: two data arrays and the relative strides. The sub returns a List of Pairs: 'data1' and the element of the first array taken with a stride $stride1, sorted in ascending order, and 'data2' and the elements of the second array taken with a stride $stride2, rearranged as the first array.
  
  For example:
  
  ```
  my @data1 = (10…0)».Num;
  my @data2 = (20…0)».Num;
  say @data1; # output: [10 9 8 7 6 5 4 3 2 1 0]
  say @data2; # output: [20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0]
  my %out = num64sort2(:@data1, :stride1(2), :@data2, :stride2(3));
  say %out<data1>; # output: (0 9 2 7 4 5 6 3 8 1 10)
  say %out<data2>; # output: (5 19 18 8 16 15 11 13 12 14 10 9 17 7 6 20 4 3 2 1 0)
  
  ```
  
  ### num64sort-index(:@data, Int :$stride? = 1 --> List)
  
  This sub indirectly sorts the elements of the array with stride into ascending order, returning the resulting permutation.
  
  ### num64sort-vector(Math::Libgsl::Vector $v)
  
  This sub sorts in place the elements of the Math::Libgsl::Vector $v into ascending numerical order.
  
  ### num64sort2-vector(Math::Libgsl::Vector $v1, Math::Libgsl::Vector $v2)
  
  This sub sorts the elements of the Math::Libgsl::Vector $v1 into ascending numerical order, while making the same rearrangement of the vector $v2.
  
  ### num64sort-vector-index(Math::Libgsl::Vector $v, Math::Libgsl::Permutation $p where $v.vector.size == $p.p.size)
  
  This sub indirectly sorts the elements of the Math::Libgsl::Vector $v, storing the resulting permutation in $p. The vector and the permutation must have the same number of elements.
  
  ### num64smallest(:@data, Int :$stride? = 1, Int :$k? where \* ≤ (@data.elems / $stride).ceiling = @data.elems --> List)
  
  This sub returns the $k smallest elements of the array, extracted with $stride, in ascending numerical order.
  
  ### num64largest(:@data, Int :$stride? = 1, Int :$k? where \* ≤ (@data.elems / $stride).ceiling = @data.elems --> List)
  
  This sub returns the $k largest elements of the array, extracted with $stride, in ascending numerical order.
  
  ### num64smallest-index(:@data, Int :$stride? = 1, Int :$k? where \* ≤ (@data.elems / $stride).ceiling = @data.elems --> List)
  
  This sub returns the indices of the $k smallest elements of the array, extracted with $stride, in ascending numerical order.
  
  ### num64largest-index(:@data, Int :$stride? = 1, Int :$k? where \* ≤ (@data.elems / $stride).ceiling = @data.elems --> List)
  
  This sub returns the indices of the $k largest elements of the array, extracted with $stride, in ascending numerical order.
  
  ### num64vector-smallest(Math::Libgsl::Vector $v, Int $k? where \* < $v.vector.size = $v.vector.size --> List)
  
  This sub returns the $k smallest elements of the vector, extracted with $stride, in ascending numerical order.
  
  ### num64vector-largest(Math::Libgsl::Vector $v, Int $k? where \* < $v.vector.size = $v.vector.size --> List)
  
  This sub returns the $k largest elements of the vector, extracted with $stride, in ascending numerical order.
  
  ### num64vector-smallest-index(Math::Libgsl::Vector $v, Int $k? where \* < $v.vector.size = $v.vector.size --> List)
  
  This sub returns the indices of the $k largest elements of the vector, extracted with $stride, in ascending numerical order.
  
  ### num64vector-largest-index(Math::Libgsl::Vector $v, Int $k? where \* < $v.vector.size = $v.vector.size --> List)
  
  This sub returns the indices of the $k largest elements of the vector, extracted with $stride, in ascending numerical order.
  
  # C Library Documentation
  
  For more details on libgsl see <https://www.gnu.org/software/gsl/>. The excellent C Library manual is available here <https://www.gnu.org/software/gsl/doc/html/index.html>, or here <https://www.gnu.org/software/gsl/doc/latex/gsl-ref.pdf> in PDF format.
  
  # Prerequisites
  
  This module requires the libgsl library to be installed. Please follow the instructions below based on your platform:
  
  ## Debian Linux
  
  ```
  sudo apt install libgsl23 libgsl-dev libgslcblas0
  
  ```
  
  That command will install libgslcblas0 as well, since it's used by the GSL.
  
  ## Ubuntu 18.04
  
  libgsl23 and libgslcblas0 have a missing symbol on Ubuntu 18.04. I solved the issue installing the Debian Buster version of those three libraries:
  
  * <http://http.us.debian.org/debian/pool/main/g/gsl/libgslcblas0_2.5+dfsg-6_amd64.deb>
  * <http://http.us.debian.org/debian/pool/main/g/gsl/libgsl23_2.5+dfsg-6_amd64.deb>
  * <http://http.us.debian.org/debian/pool/main/g/gsl/libgsl-dev_2.5+dfsg-6_amd64.deb>
  
  # Installation
  
  To install it using zef (a module management tool):
  
  ```
  $ zef install Math::Libgsl::Sort
  
  ```
  
  # AUTHOR
  
  Fernando Santagata [nando.santagata@gmail.com](mailto:nando.santagata@gmail.com)
  
  # COPYRIGHT AND LICENSE
  
  Copyright 2020 Fernando Santagata
  
  This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.
  