As part of code review of !162 we identified that functions such as `vcl_abs` are not really need anymore. There are [defined to their std equivalents](https://github.com/InsightSoftwareConsortium/ITK/blob/master/Modules/ThirdParty/VNL/src/vxl/vcl/vcl_compiler.h#L339) in ITK master branch. See also ITK commit [21334467](https://github.com/InsightSoftwareConsortium/ITK/commit/2133446772e6a688e25cbfb1b74bb709103fe77f): > ENH: Avoid using vnl_math_ functions > > In order to isolate ITK from vnl_math_ functions an aliasing > system is created to prefer to use itk::Math:: functions > over the vnl_math_ versions. This is partially precipated by > a need to provide backwards compatibility with vnl_math_ prior > to the introduction of the vnl_math:: namespace so that > we can consistently use it. > > Recent cleanup of the vxl codebase identified that modern > supported compilers do not need most of the aliasing infrastructure > of vxl/vnl/vcl and that in many cases functions simply degrade to > the std:: versions. In order to minimize dependancies, and to > assist new users of ITK to more naturally understand the code, > we prefer to use the std:: versions whenever possible. > > In particular, there is no benefit to using vnl_math_min or > vnl_math_max functions that always degenerated to equivalent > functionality as std::min and std::max. Since the std:: versions > are more universally understood and known by most developers, > we prefer to use these common versions. It seems like we could use `std::` functions most of the time?