[tex-k] Erratum: MF: The Program, pp.387-389 & mf: help suggesting `???' without checking if plain.base is being used

[Dominik Leininger]

Hello everyone,

In the sections 872, 873 and 878, the help refers to chapter 27 of The 
MFbook and suggests to use the `???' macro defined in plain.tex without 
checking if plain is used as a base file or if a different base file is 
loaded. Of course a different base file might not define `???' and the 
user may be confused by the additional error if they follow the suggestion.

I suggest adding ` if you are using plain METAFONT' between `now' and 
the period in lines 17441, 17461, 17471, 17546 and 17564 of mf.web. An 
alternative is to implement a check if plain.base is used and only print 
the lines `(Chapter 27 of The METAFONTbook explains that' and ``you 
might want to type `I ???' now.)'' if it is loaded.

Best regards,

Dominik