[erlang-bugs] erl rejects FQN that begin with a digit

[Raimo Niskanen]

On Wed, Oct 20, 2010 at 02:37:45PM +0200, Vlad Dumitrescu wrote:
> On Wed, Oct 20, 2010 at 14:13, Patrick Baggett
> <baggett.patrick@REDACTED> wrote:
> > -- snip --
> > 2.3  Atom
> > An atom is a literal, a constant with name. An atom should be enclosed in
> > single quotes (') if it does not begin with a lower-case letter or if it
> > contains other characters than alphanumeric characters, underscore (_), or
> > @.
> > -- snip --
> >  name@REDACTED contains a @, so one would expect if this was a single atom, that
> > single quotes would be required, but they aren't. Erlang just magically
> > knows, that is, unless you start it with a digit, because when it is broken
> > into multiple atoms (I guess?) it fails the test of starting with a lower
> > case character.
> 
> It's not the @ that separates the name in multiple atoms, but the
> dots. It's an artifact of the still experimental package feature that
> you can chain atoms together with dots, in the old times one had to
> use quotes for host names.

Long host names that is. foo@REDACTED has always been interpreted as an atom.
That was a peculiar side effect of the package system. The traditional
answer is: node names with fully qualified host names has to be quoted
in whole e.g 'foo@REDACTED'.

> 
> >  But if it starts with a digit, then it needs quotes, /around the whole
> > thing/, meaning it isn't a sequence of atom@REDACTED, but just 'atom'
> > I would have expected to see host1@'8fun'.net, which makes '8fun' an atom,
> > rather than the whole thing.
> 
> No, quotes around the misbehaving atom work fine:
> 
> 1> x@REDACTED
> x@REDACTED
> 2> x@REDACTED
> x@REDACTED
> 4> x@REDACTED
> * 1: syntax error before: 2
> 4> x@REDACTED'2y'.
> 'x@REDACTED'
> 
> regards,
> Vlad
> 
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-- 

/ Raimo Niskanen, Erlang/OTP, Ericsson AB