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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA
//
// 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 [t] = acosh(z)
//
// PURPOSE
// element wise hyperbolic arccosinus
//
// METHOD
// based on the formula :
//
// acosh(z) = sign(-imag(acos(z)) i acos(z)
//
// but as in Scilab sign(0) = 0 (and this don't
// work in the formula which needs sign(0)=1)
// the following slower trick is used :
//
// sign(-x) = 2*(0.5 - bool2s(x>0))
//
rhs = argn(2);
if rhs <> 1 then
error(msprintf(gettext("%s: Wrong number of input argument(s): %d expected.\n"),"acosh",1));
end
if type(z)<>1 then
error(msprintf(gettext("%s: Wrong type for input argument #%d: Real or complex matrix expected.\n"),"acosh",1));
end
if isreal(z) then
if min(z) < 1 then
// result is complex
u = acos(z)
t = 2*(0.5 - bool2s(imag(u)>0)).*imult(u)
else
// result is real
t = imag(acos(z));
t(isnan(z)) = %nan;
end
else
u = acos(z)
t = 2*(0.5 - bool2s(imag(u)>0)).*imult(u)
end
endfunction
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