C++17 and Boost generates an error for unary_function in external submodule

[joshkellyjak]

Reporting here in case anyone encounters this issue in future. In C++ 17 the function std::unary_function was discontinued, there is one line in the boost library of tecio that uses this and causes a compilation error (at least on MacOS). The solution is very simple and this can be resolved by changing the function to std::__unary_function. I have observed this and it has also been encountered by at least one other.

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[pcarruscag]

Pull request with the easy fix?

[joshkellyjak]

Will do later this week but think updating the library maybe makes more sense. I guess the tecplot guys have already encountered this so may be worth reaching out. I assume I can't upload the customer library directly to GitHub