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########################################################################
##
## Copyright (C) 1993-2024 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {@var{p} =} list_primes ()
## @deftypefnx {} {@var{p} =} list_primes (@var{n})
## List the first @var{n} primes.
##
## If @var{n} is unspecified, the first 25 primes are listed.
## @seealso{primes, isprime}
## @end deftypefn
function p = list_primes (n = 25)
if (! isreal (n) || ! isscalar (n))
error ("list_primes: N must be a real scalar");
endif
n = floor (n);
if (n < 1)
p = [];
return;
elseif (n == 1)
p = 2;
return;
endif
list = primes (n * log (5 * n));
if (numel (list) < n)
## Algorithm tested up to n=10,000 without failure.
error ("list_primes: Algorithm failed. Try primes (n*log (6*n))(1:n)");
endif
p = list(1:n);
endfunction
%!assert (list_primes (), [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, ...
%! 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97])
%!assert (list_primes (5), [2, 3, 5, 7, 11])
%!assert (list_primes (0), [])
%!assert (list_primes (1), [2])
## Test input validation
%!error <N must be a real scalar> list_primes (i)
%!error <N must be a real scalar> list_primes ([1 2])
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