Gene, In a LON-CAPA script block a call to &tanh() will use the tanh() function provided by Math::Cephes, which only supports real numbers.
The Math::Cephes::Complex package, which does support complex numbers, has a ctanh() function, but Math::Cephes::Complex is not currently available within LON-CAPA's perl safe space (where code within a script block in a LON-CAPA problem is evaluated). Support for complex numbers in LON-CAPA's perl safe space is currently made available via the LONCAPA::LCMathComplex package, which is the standard Math::Complex module available from CPAN, but modified to work in Safe Space. Where there is no overlap with function names used for Math::Cephes functions, then you can just use the LCMathComplex functions directly, e.g.. &cplx(), &Re(), &Im(), but where there is overlap, as is the case for tanh(), to ensure the function from LCMathComplex is called, include the full namespace identifier, e.g., &LONCAPA::LCMathComplex::tanh(). For the future I can add a set of unique function names to LON-CAPA for those functions in LCMathComplex which overlap with function names in Math::Cephes, and then you could just call those without needing a full namespace identifier. Anyway, as things stand today, the code below will display both real and imaginary parts for the hyperbolic tan -- tanh -- for a complex number (in this case 3 + 4i ) <script type="loncapa/perl"> $z = &cplx(3, 4); $x = &LONCAPA::LCMathComplex::tanh($z); $tanh_real = &Re($x); $tanh_imag = &Im($x); </script> <startouttext /> tanh($z) is $x <br /> The real part is: $tanh_real <br /> The imaginary part is: $tanh_imag <br /> <endouttext /> Stuart Raeburn LON-CAPA Academic Consortium ________________________________________ From: LON-CAPA-users <lon-capa-users-boun...@mail.lon-capa.org> on behalf of Harding, Gene L <glhar...@purdue.edu> Sent: Wednesday, January 29, 2020 6:42 PM To: Discussion list for LON-CAPA users Subject: [LON-CAPA-users] Hyperbolic Trig Function Problem Hi, Does anyone have experience using the hyperbolic trig functions in LON-CAPA? I have recently been coding some new problems that use the &tanh() function. I was comparing the results to those I got using MATLAB, and after some troubleshooting it appears that the difference is the tanh. Specifically, the &tanh($x) function in LON-CAPA always returns an imaginary value of zero. Here is the code: $tanh = &tanh($gamma*$len); $tanh_real = Re($tanh); $tanh_imag = Im($tanh); where $gamma is a complex number and $len is a scalar. MATLAB computes a complex number for tanh in the examples I have tried. Am I doing something wrong? Does LC not compute tanh correctly? Best regards, Gene L. Harding, PE Associate Professor of ECET Purdue University 574-520-4190 _______________________________________________ LON-CAPA-users mailing list LON-CAPA-users@mail.lon-capa.org http://mail.lon-capa.org/mailman/listinfo/lon-capa-users
