Suppose we're going to construct a container, and need combining traits at the compile time. There are some ways to make it, for example, we may use several bools
To use that code will become some sort of nightmare, since every parameter is a bool, if you make a mistake on the order of arguments, you could hardly discover it before the program goes mad.
Another approach is, to merge all bools to a single unsigned, like
But that is not good too, since in the first place we have to define some flags
and then to use those flags, say, consider we add an insert interface to the container, which is concerned about whether or not allows duplicated elements in the container, the code may look like
However unfortunately that won't compile, because C++ forbid specialize template functions (whether partial or not). So, we have to put that _insert into a template struct, like
That looks really weird, and for struct insert_s, It should be granted public access to just_a_container.
Besides, in the code there would be full of bitwise-and here and there like