Re: GNAT's Text_IO & empty files

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Markus says

<<Having just read RM A.10 M-'7, I think the Ada standard is badly
  formulated here. It is not clear how a file or a page with zero
  lines or a file with zero pages has to be encoded. The standard writes
  that a file is a sequence of pages and a page is a sequence of lines,
  but it does not handle the obvious border case of zero-length
  sequences adequatly. It would have been better to write just that
  every line terminates with a line terminator, and every page
  terminates with a page terminator, and then everything would have
  been clear and consistent. With a bit good will, the Ada RM language
  can even be interpreted that way.>>


I disagree. The RM deliberately stays out of the business of describing
how a file is encoded, and that is as it should be, since the appropriate
encoding is most certainly system dependent. It just describes a set of
high level features, and you can implement them anyway you want. People
often assume for instance that the codes in a Text_IO file will match
those of Standard.Character, but nowhere in the RM is there such a
requirement, and a compiler that always used Unicode for Text_IO files
is perfectly well conforming!