hmm, I did this according to https://github.com/ethz-asl/programming_styleguide/wiki/Cpp-Coding-Style-Guidelines#9-names-representing-template-parameters-should-be-named-like-types-but-with-an-trailing-underscore-or-with-a-single-capital-letter-in-case-there-are-few-arguments-and-their-meaning-is-clear