---
name: "Math::GSL::Combination"
section: "3pm"
platform: "linux"
package: "libmath-gsl-perl"
version: "0.45-2+b1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Math::GSL::Combination"
---

# Math::GSL::Combination(3pm)

Combinations

## NAME

Math::GSL::Combination - Combinations

## SYNOPSIS

```
    use Math::GSL qw/:all/;
    use Math::GSL::Combination qw/:all/;
    my $c   = Math::GSL::Combination->new(6,3);
    print join (" ", $c->as_list) . "\n";
    $c->next;
    print join (" ", $c->as_list) . "\n";
    my $fd = gsl_fopen('combination.dat', 'w');
    gsl_combination_fwrite($fd, $c->raw);
    gsl_fclose($fd);
```

## DESCRIPTION

Here is a list of all the functions in this module :

- •

  `"gsl_combination_alloc($n, $k)"`

  This function allocates memory for a new combination with parameters `$n`, `$k`. The combination is not initialized and its elements are undefined. Use the function gsl\_combination\_calloc if you want to create a combination which is initialized to the lexicographically first combination.

- •

  `"gsl_combination_calloc($n, $k)"`

  This function allocates memory for a new combination with parameters `$n`, `$k` and initializes it to the lexicographically first combination.

- •

  `gsl_combination_init_first($c)`

  This function initializes the combination `$c` to the lexicographically first combination, i.e. (0,1,2,...,k-1).

- •

  `gsl_combination_init_last($c)`

  This function initializes the combination `$c` to the lexicographically last combination, i.e. (n-k,n-k+1,...,n-1).

- •

  `gsl_combination_free($c)`

  This function frees all the memory used by the combination `$c`.

- •

  `"gsl_combination_memcpy($dest, $src)"`

  This function copies the elements of the combination `$src` into the combination `$dest`. The two combinations must have the same size.

- •

  `"gsl_combination_get($c, $i)"`

  This function returns the value of the i-th element of the combination `$c`. If `$i` lies outside the allowed range of 0 to k-1 then the error handler is invoked and 0 is returned.

- •

  `"gsl_combination_fwrite($stream, $c)"`

  This function writes the elements of the combination `$c` to the stream `$stream`, opened with the gsl\_fopen function from the Math::GSL module, in binary format. The function returns `$GSL_EFAILED` if there was a problem writing to the file. Since the data is written in the native binary format it may not be portable between different architectures.

- •

  `"gsl_combination_fread($stream, $c)"`

  This function reads elements from the open stream `$stream`, opened with the gsl\_fopen function from the Math::GSL module, into the combination `$c` in binary format. The combination `$c` must be preallocated with correct values of n and k since the function uses the size of `$c` to determine how many bytes to read. The function returns `$GSL_EFAILED` if there was a problem reading from the file. The data is assumed to have been written in the native binary format on the same architecture.

- •

  `"gsl_combination_fprintf($stream, $c, $format)"`

  This function writes the elements of the combination `$c` line-by-line to the stream `$stream`, opened with the gsl\_fopen function from the Math::GSL module, using the format specifier `$format`, which should be suitable for a type of size\_t. In ISO C99 the type modifier z represents size\_t, so "%zu\\n" is a suitable format. The function returns `$GSL_EFAILED` if there was a problem writing to the file.

- •

  `"gsl_combination_fscanf($stream, $c)"`

  This function reads formatted data from the stream `$stream` into the combination `$c`. The combination `$c` must be preallocated with correct values of n and k since the function uses the size of `$c` to determine how many numbers to read. The function returns `$GSL_EFAILED` if there was a problem reading from the file.

- •

  `gsl_combination_n($c)`

  This function returns the range (n) of the combination `$c`.

- •

  `gsl_combination_k($c)`

  This function returns the number of elements (k) in the combination `$c`.

- •

  `gsl_combination_data($c)`

  This function returns a pointer to the array of elements in the combination `$c`.

- •

  `gsl_combination_valid($c)`

  This function checks that the combination `$c` is valid. The k elements should lie in the range 0 to n-1, with each value occurring once at most and in increasing order.

- •

  `gsl_combination_next($c)`

  This function advances the combination `$c` to the next combination in lexicographic order and returns `$GSL_SUCCESS`. If no further combinations are available it returns `$GSL_FAILURE` and leaves `$c` unmodified. Starting with the first combination and repeatedly applying this function will iterate through all possible combinations of a given order.

- •

  `gsl_combination_prev($c)`

  This function steps backwards from the combination `$c` to the previous combination in lexicographic order, returning `$GSL_SUCCESS`. If no previous combination is available it returns `$GSL_FAILURE` and leaves `$c` unmodified.

## MORE INFO

For more information on the functions, we refer you to the GSL official documentation: \<http://www.gnu.org/software/gsl/manual/html\_node/\>

## AUTHORS

Jonathan "Duke" Leto \<jonathan@leto.net\> and Thierry Moisan \<thierry.moisan@gmail.com\>

## COPYRIGHT AND LICENSE

Copyright (C) 2008-2024 Jonathan "Duke" Leto and Thierry Moisan

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.