[bug #59031] the \[Im] and \[Re] escapes are wrong

[Ingo Schwarze]

Update of bug #59031 (project groff):

              Item Group:           Documentation => Incorrect behaviour    
                  Status:             In Progress => Need Info              

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Follow-up Comment #4:

You were explicitly talking about *sets*, so i made it clear that these
symbols do not represent sets but functions.  The reason that the word
"function" is not in groff_char(7) is probably just that there is not enough
space.  Mentioning the "Gothic" is more important,  because with "Gothic" the
"function" is clear.  With "function" or "part" but without "Gothic", it would
not be clear which glyph these produce because as you say, there are different
possibilities to represent these functions (but *if* the Gothics are used in
the context of complex numbers, their meaning is clear).

All three of your points are wrong.
1. The descriptions are correct and clear.
2. Representing these function with Gothic is a valid choice.
3. The glyph names are not wrong.  The Gothic R and I symbols are commonly
read aloud as "Re" and "Im".  These symbols do not indicate sets and the
symbols do not imply that.  Your parenthetic remark makes no sense to me, but
most definitely C is not the same as iR in any sense.

All your solutions are wrong, too.
A. Breaks compatibility and removes useful functionality for no reason
whatsoever.
B. is just outrageously wrong.  \(Re, i.e. the Re() function, is never
represented with a double-struck R, and the field of real numbers is never
called "Re"; when read, it is "er".  Besides, U+221D is "PROPORTIONAL TO". 
\(Im is never represented with a double-struck I.  Even iR is usually not
represented with a double-struck I because it does not form a ring (is not
closed under multiplication).  Double-struck letters are commonly used for
sets having a structure (like a field, ring, whatever), not for bare sets.
C. also breaks compatibility and functionality for no reason.  There is no
error.
D. is the correct solution, except that nothing is wrong.

If you want to represent Re() and Im() as Re() and Im() in your printed
formula, which, as you say, is indeed one valid choice, you can simply put the
strings "Re(" etc. into your roff(7) source and don't need any escapes.  But
if you want the Gothics, the escapes are needed to keep the source readable.

So please, just drop this already.

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