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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA - Farid BELAHCENE
// Copyright (C) DIGITEO - 2011 - Allan CORNET
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
function y=factor(x)
// FACTOR function
// Given a real x , this function returns a vector whose the components are the primes factors of the x decompositon.
// Particular cases:
// if x=0, then returns 0
// if x=1, then return 1
// Inputs :
// x : a real scalar (positive)
// output :
// y : a vector of primes numbers
rhs = argn(2);
if rhs <> 1 then
error(msprintf(gettext("%s: Wrong number of input argument(s): %d expected.\n"),"factor", 1));
end
if prod(size(x,"*"))<>1 then
error(msprintf(gettext("%s: Wrong size for input argument #%d: An integer expected.\n"),"factor",1));
elseif(type(x)<>1) then
error(msprintf(gettext("%s: Wrong type for input argument #%d: An integer expected.\n"),"factor",1));
elseif x<0 | x-floor(x)<>0
error(msprintf(gettext("%s: Wrong value for input argument #%d: Scalar positive integer expected.\n"),"factor",1));
elseif or(x==[0 1 2 3])
y=x
else
xprimefact = primes(sqrt(x))
y = []
while x > 1
xdiv = x ./ xprimefact
xprimefact_ind = find(xdiv-floor(xdiv)==0)
if xprimefact_ind <> []
xprimefact = xprimefact(xprimefact_ind)
y = [xprimefact y]
x = x/prod(xprimefact)
else
y=[x y]
break
end
end
end
y = gsort(y,"c","i")
endfunction
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