new file mode 100644
--- /dev/null
+++ b/doc/interpreter/mk_doc_cache.m
@@ -0,0 +1,122 @@
+## Copyright (C) 2009 John W. Eaton
+##
+## This program is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## This program is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+args = argv ();
+
+if (nargin < 2)
+  error ("usage: mk_doc_cache OUTPUT-FILE DOCSTRINGS-FILE ...");
+endif
+
+output_file = args{1};
+docstrings_files = args(2:end);
+
+doc_delim = char (31);
+
+function str = skip_newline (str)
+  n = numel (str);
+  j = 1;
+  while (j <= n)
+    c = str(j);
+    if (c == "\r" || c == "\n")
+      j++;
+    else
+      break;
+    endif
+  endwhile
+  str = str(j:end);
+endfunction
+
+doc_cache = [];
+
+for i = 1:numel (docstrings_files);
+
+  file = docstrings_files{i};
+
+  fid = fopen (file, "r");
+
+  if (fid < 0)
+    error ("unable to open %s for reading", file);
+  else
+
+    printf ("processing %s\n", file);
+
+    text = fread (fid, Inf, "*char")';
+
+    delim_idx = find (text == doc_delim);
+    eof = numel (text);
+    idx = [delim_idx, eof];
+
+    n = numel (delim_idx);
+
+    tmp_doc_cache = cell (3, n);
+    k = 1;
+
+    for i = 1:n
+
+      tmp = text(idx(i)+1:idx(i+1)-1);
+
+      [symbol, doc] = strtok (tmp, "\r\n");
+
+      doc = skip_newline (doc);
+
+      ## Skip functions that start with __ as these shouldn't be
+      ## searched by lookfor.
+      if (numel (symbol) > 2 && regexp (symbol, "^__.+__$"))
+	continue;
+      endif
+  
+      printf ("  %s\n", symbol);
+
+      if (strncmp (doc, "-*- texinfo -*-", 15))
+	doc = skip_newline (doc(16:end));
+      else
+	error ("doc string for %s is not in texinfo format", symbol);
+      endif
+
+      [formatted_text, status] = makeinfo (doc, "plain text");
+    
+      ## Did we get the help text?
+      if (status != 0 || isempty (formatted_text))
+	error ("makeinfo failed for %s doc string", symbol);
+      endif
+
+      ## Extract first line by searching for a period or a double
+      ## line-end.
+
+      period_idx = find (formatted_text == ".", 1);
+
+      line_end_idx = strfind (formatted_text, "\n\n");
+
+      max_first_sentence_len = 80;
+
+      first_sentence = formatted_text (1:min ([period_idx(:); line_end_idx(:); max_first_sentence_len; numel(formatted_text)]));
+
+      tmp_doc_cache{1,k} = symbol;
+      tmp_doc_cache{2,k} = formatted_text;
+      tmp_doc_cache{3,k} = first_sentence;
+      k++;
+
+    endfor
+
+    tmp_doc_cache(:,k:end) = [];
+
+  endif
+
+  doc_cache = [doc_cache, tmp_doc_cache];
+
+  save ("-text", output_file, "doc_cache");
+
+endfor