Using %printer

[Frans Englich]

The Bison manual for 2.3 use %printer but doesn't describe it.

How does on use %printer?

Will it change much in 2.4?

What exactly does it do, it allows one to at runtime customize the message 
Bison uses for a token(and perhaps even terminal?)? For example, that instead 
of that Bison says "Unexpected <numeric literal>" one can make it 
say "Unexpected '2.3'", right?

I'm trying to determine whether it's worth to start using it before 2.4, and 
if so, /how/ to use it ;-)


Cheers,

                Frans