Differentiate overloaded constructors

Sometimes you want to overload constructors, but discover that the argument types you want to use are not sufficient to differentiate those constructors. A good solution is to use a lightweight (inline) nested class to wrap constructor arguments in a distinct type that's easy to overload. For example, in the Graphics system, one early design for TGrafMatrix had constructors that were similar to:

      TGrafMatrix(const Translate &);
      TGrafMatrix(const Rotate &);
      TGrafMatrix(const Scale &);
The three argument types are nested classes whose constructors take appropriate arguments. A call to create a translation matrix looks like this:

Eventually, with name spaces, the helper classes might not have to be nested, which will make this kind of construct easier to type.

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