Thank you! Did you try different compilers? Do you know which one works?
To patch it up I now used std::experimental::optional with which it seems to compile properly.
The next problem I got with /solve/python_solve.cpp:
I changed the following lines to avoid an error:
330: "if constexpr(is_simd)" into " if (is_simd)"
and
335: "if constexpr(!is_complex)" to "if(!is_complex)"
Afterwards I get the following error:
Code:
/ngsuite/ngsolve-src/solve/python_solve.cpp:337:21: error: ‘class
ngfem::BaseMappedIntegrationRule’ has no member named ‘TransformGradientTrans’
mir.TransformGradientTrans(values);
I thought the quickest way to solve it would be a cast of mir to SIMD_BaseMappedIntegrationRule, but this gives quit a few errors as well. Do you have an idea for a quick solution for this?