Re: search-whitespace-regexp

["Chong Yidong" <cyd@stupidchicken.com>]

Let me try to explain my idea more clearly.

Since RMS has raised the issue of incompatibility, I think the default
behavior for isearch should be left as it was in 21.3, for the moment. In
other words, regexp search has a magic space, and string search doesn't.
However, there should be a way for the user to customize this.

It is relatively easy for a user to get rid of the magic space for regexp
search, if he wants to:
  (setq search-whitespace-regexp nil)

However, there is no easy way for a user to turn on the magic space for
string search; you have to hack isearch.el to do it. I suggest
implementing an analogous mechanism for string search (I'm not certain
what the variable should be called, though):

  (defvar search-string-whitespace-regexp nil
  "If non-nil, regular expression to match a sequence of whitespace chars.
  This applies to ordinary incremental search.
  You might want to use something like "[ \t\r\n]+" instead.")

Because the default is nil, there is no magic space, and the behavior is
like 21.3 and below; but users or Lisp libraries can set it as needed. For
example, longlines.el can set it to "[ \n]" so that linebreaks and spaces
are treated equally.