The ANSI-CL/CLtL2 specification for the ~<newline> format directive
reads as follows:
"Tilde immediately followed by a newline ignores the newline
and any following non-newline whitespace characters.
With a COLON,
the newline is ignored,
but any following whitespace is left in place.
With an AT-SIGN,
the newline is left in place,
but any following whitespace is ignored."
The above line should read
"but any following NON-NEWLINE whitespace characters are ignored."
I have already encountered one CL implementation (ACL/Win, formerly
Procyon CL) that seems to misinterpret the spec as written by also
ignoring newlines in any following whitespace.
References
==========
You can find the CLtL2 ~<newline> spec (same as ANSI) in
http://www.cs.cmu.edu/afs/cs.cmu.edu/project/ai-repository/ai/html/cltl/clm/node200.html
The relevant ANSI section (22.3.2 100) should be in the GNU CL html
translation, e.g. (surprisingly there appears to be no U.S. source)
http://www.econ.hku.hk/docs/gnu/gcl/gcl_22.html
but it appears that the latex to html translation has somehow omitted
the ~<newline> section. Has anyone seen similar problems? In any case,
it can be found in the the file "concept-format.tex", e.g.
http://ftp.std.com/obi/Standards/CommonLisp/dpANS2/concept-format.tex
-Bill