Re: should search ring contain duplicates?

[storm@cua.dk (Kim F. Storm)]

Dan Nicolaescu <dann@ics.uci.edu> writes:

> 	    (when history-delete-duplicates
> 	      (setq regexp-search-ring (delete string regexp-search-ring)))
> 	    (push string regexp-search-ring)
> 	    (if (> (length regexp-search-ring) regexp-search-ring-max)
> 		(setcdr (nthcdr (1- search-ring-max) regexp-search-ring)
> 			nil))))

IMO, that would be a very good candidate for a standard macro
in subr.el.  

There are several places which does this (or should do it -- but
actually doesn't get this right!):

   (history-push ELT HIST &optional LENGTH KEEPDUPS)

Default for LENGTH would be history-length, but it should also look at
the history-length property of HIST.

If KEEPDUPS is t, ignore value of history-delete-duplicates.

This would make it easy for Lisp code to do the same history
manipulation as C code:

      if (NILP (histval)
	  || (CONSP (histval)
	      /* Don't duplicate the most recent entry in the history.  */
	      && (keep_all
		  || NILP (Fequal (histstring, Fcar (histval))))))
	{
	  Lisp_Object length;

	  if (history_delete_duplicates) Fdelete (histstring, histval);
	  histval = Fcons (histstring, histval);
	  Fset (Vminibuffer_history_variable, histval);

	  /* Truncate if requested.  */
	  length = Fget (Vminibuffer_history_variable, Qhistory_length);
	  if (NILP (length)) length = Vhistory_length;
	  if (INTEGERP (length))
	    {
	      if (XINT (length) <= 0)
		Fset (Vminibuffer_history_variable, Qnil);
	      else
		{
		  Lisp_Object temp;

		  temp = Fnthcdr (Fsub1 (length), histval);
		  if (CONSP (temp)) Fsetcdr (temp, Qnil);
		}
	    }
	}


-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk