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Boost Users : |
From: John Maddock (jz.maddock_at_[hidden])
Date: 2020-08-16 11:50:49
On 14/08/2020 22:56, Anirban Pal via Boost-users wrote:
> Hello,
>
> I'm trying to integrate functions with BOOST quadrature routines. So
> far they have been extremely impressive accuracy-wise, particularly
> with multiprecision features.
>
> I wish to integrate a function and pass some arguments to it. These
> arguments can be scalars, matrices, structs or objects. I was
> wondering if there is an example that explores this. Would I need to
> use a boost.function? Or would a function pointer work?
To create a reusable single-valued functor that integrates from [a, x]
for fixed a, then I think some nested lambda expressions would work:
  auto integral = [](double x)
  { // Integrates from 0 to x:
     static tanh_sinh<double> integrator;
     static auto f = [](double x) { return 5 * x + 7; };
     return integrator.integrate(f, 0.0, x);
  };
  std::cout << integral(2) << std::endl;
  std::cout << integral(4.5) << std::endl;
I'm not sure what you had in mind with non-scalar arguments, but if you
need to evaluate the above at multiple x values [x_1, x_2.... x_n] then
conceivably you could integrate from
[a, x_0]
[x_1, x_2]
....
[x_n-1, x_n]
and then sum to get the integrals
[a, x_0]
[a, x_1]
....
[a, x_n]
Which may or may not be more efficient.
HTH, John.
>
> I currently have an implementation using GSL_functions which
> explicitly allow the function and parameters to be passed as pointers.
> I am curious if I can do something similar with boost.
>
> Thank you.
>
>
> --
> Anirban Pal
>
>
>
>
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