Re: Difficulty using boost quadrature library

From: John Maddock (jz.maddock_at_[hidden])
Date: 2020-08-14 10:22:56

On 14/08/2020 01:07, Anirban Pal via Boost-users wrote:
> 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:
>
> <goog_14736225>
> https://www.boost.org/doc/libs/1_66_0/libs/math/doc/html/math_toolkit/double_exponential/de_tanh_sinh.html 
> <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 confess that's not the best example in the docs :(

The name "Real" is just used as "some kind of floating point type" - 
replace with whatever actual type you wish to use.

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