${parameter+word} not documented in bash.info or bash(1)

[Martin Schwenke]

I'm running bash 3.2.39(1)-release (under Ubuntu 8.04 (Hardy)
GNU/Linux).  Neither bash.info or bash(1) documents parameter
expansion of the form:

  ${parameter+word}

This is different to ${parameter:+word}, is clearly implemented by
bash and is documented in the standard (The Open Group Base
Specifications Issue 6, IEEE Std 1003.1, 2004 Edition).

This may be useful:

  
http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_02

Thanks for bash, it rocks...  :-)

peace & happiness,
martin