[Groff] C++ solution of the char length problem

[Bernd Warken]

We had already some discussions on the bad handling of the length of
character variables in groff.  The C solution uses a cumbersome
preprocessor construct.  Fortunately, there is a possibility to handle
the variable length with an excellent C++ solution, that is even
available in all versions of C++, but not in plain C.

The member in a `struct' or `class' can be enhanced by a so-called
"bit-field", a `:' separated length argument appended to the variable
name.  For example, a 8 bits integer could be defined as

struct Int8 {
  int data: 8;
}

or

class Int8 {
  int data: 8;
  ...
}


Usually, groff uses positive values for normal characters, and
negative values for special groff properties.  So groff uses signed
variables for representing characters.  This doubles the necessary
space.

When we are using a `struct' or `class' anyway, this can be optimized
by an additional Boolean member.  For example, a groff Unicode
character type could be defined as

class GroffChar {
  unsigned int data: 16;
  bool special;
public:
  ...
}

This will be especially helpful for the increasing number of handheld
computers with small standard space.

I will not have the time to do this for groff, so feel free to use
this as you like.

Bernd Warken