You need to decide on which Real type you want, perhaps

#include <boost/multiprecision/cpp_bin_float.hpp>

and then chose perhaps a quad precision type like cpp_bin_float_quad for 128-bit precision

You can then either use a typedef to define Real

typedef cpp_bin_float_quad Real;

or pass cpp_bin_float_quad as a template parameter into your own function.

HTH

Paul

PS It would be nice if we had a fully worked example?

From: Boost-users <boost-users-bounces@lists.boost.org> On Behalf Of Anirban Pal via Boost-users
Sent: 14 August 2020 01:08
To: boost-users@lists.boost.org
Cc: Anirban Pal <anirban.pal.iitkgp@gmail.com>
Subject: [Boost-users] Difficulty using boost quadrature library

Hello everyone,

I'm new to using boost and I'm trying to use its quadrature routines, specifically

the tanh_sinh integrator. I'm trying to run the examples here:

https://www.boost.org/doc/libs/1_66_0/libs/math/doc/html/math_toolkit/double_exponential/de_tanh_sinh.html

I've been successful using it with the double datatype. However, I can't seem to work with the Real datatype. When I run the following, I'm successful.

tanh_sinh<double> integrator;
auto f = [](double x) { return 5*x + 7; };
double Q = integrator.integrate(f);
Q = integrator.integrate(f, 0.0, 1.1);

But when I run the following:

auto f = [](Real x) { return log(x)*log(1-x); };
Real Q = integrator.integrate(f, (Real) 0, (Real) 1);

I get the error:

boost_test.cxx: In function ‘int main(int, char**)’:
boost_test.cxx:47:15: error: ‘Real’ has not been declared
  auto f2 = [](Real x) { return log(x)*log(1-x); };
               ^~~~
boost_test.cxx:48:2: error: ‘Real’ was not declared in this scope
  Real Q2 = integrator.integrate(f2, (Real) 0, (Real) 1);

I think I need to include the right headers for this to go away. However, I'm not sure what the correct header file is.

Thank you for your attention.

--

Anirban Pal