// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA, Serge Steer
// 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 = asech(x)

    //Inverse hyperbolic secant
    //asech(x)=  arccosh(1 ./ x)= i*csgn(i*(1−1 ./ x))*asec(x)=csgn(i*(1 − 1 ./ x))*(%pi/2*(i+acsch(i*x)))

    rhs = argn(2);
    if rhs <> 1 then
        error(msprintf(gettext("%s: Wrong number of input argument(s): %d expected.\n"),"asech", 1));
    end
    
    if and(type(x) <> [1 5]) then
        error(msprintf(gettext("%s: Wrong type for input argument #%d: Real or complex, sparse or full matrix expected.\n"),"asech", 1));
    end

    y = acosh(ones(x)./x);
endfunction