Prefer transparent functors to non-transparent ones. When using transparent functors, the type does not need to be repeated. The code is easier to read, maintain and less prone to errors. It is not possible to introduce unwanted conversions.

// Non-transparent functor
std::map<int, std::string, std::greater<int>> s;

// Transparent functor.
std::map<int, std::string, std::greater<>> s;

// Non-transparent functor
using MyFunctor = std::less<MyType>;

It is not always a safe transformation though. The following case will be untouched to preserve the semantics.

// Non-transparent functor
std::map<const char *, std::string, std::greater<std::string>> s;



If the option is set to non-zero, the check will not diagnose cases where using a transparent functor cannot be guaranteed to produce identical results as the original code. The default value for this option is 0.

This check requires using C++14 or higher to run.