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## Copyright (C) 2009-2013 Søren Hauberg
##
## This file is part of Octave.
##
## Octave 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.
##
## Octave 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 Octave; see the file COPYING. If not, see
## <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {[@var{text}, @var{status}] =} get_first_help_sentence (@var{name})
## @deftypefnx {Function File} {[@var{text}, @var{status}] =} get_first_help_sentence (@var{name}, @var{max_len})
## Return the first sentence of a function's help text.
##
## The first sentence is defined as the text after the function
## declaration until either the first period (".") or the first appearance of
## two consecutive newlines ("\n\n"). The text is truncated to a maximum
## length of @var{max_len}, which defaults to 80.
##
## The optional output argument @var{status} returns the status reported by
## @code{makeinfo}. If only one output argument is requested, and @var{status}
## is non-zero, a warning is displayed.
##
## As an example, the first sentence of this help text is
##
## @example
## @group
## get_first_help_sentence ("get_first_help_sentence")
## @print{} ans = Return the first sentence of a function's help text.
## @end group
## @end example
## @end deftypefn
function [text, status] = get_first_help_sentence (name, max_len = 80)
## Check input
if (nargin < 1 || nargin > 2)
print_usage ();
endif
if (!ischar (name))
error ("get_first_help_sentence: NAME must be a string");
endif
if (! isnumeric (max_len) || max_len <= 0 || max_len != fix (max_len))
error ("get_first_help_sentence: MAX_LEN must be positive integer");
endif
## First, we get the raw help text
[help_text, format] = get_help_text (name);
## Then, we take action depending on the format
switch (lower (format))
case "plain text"
[text, status] = first_sentence_plain_text (help_text, max_len);
case "texinfo"
[text, status] = first_sentence_texinfo (help_text, max_len);
case "html"
[text, status] = first_sentence_html (help_text, max_len);
case "not documented"
error ("get_first_help_sentence: '%s' is not documented\n", name);
case "not found"
error ("get_first_help_sentence: '%s' not found\n", name);
otherwise
error ("get_first_help_sentence: internal error: unsupported help text format: '%s'\n", format);
endswitch
if (nargout <= 1 && status != 0)
warning ("get_first_help_sentence: couldn't run makeinfo on '%s'", name);
endif
endfunction
## This function extracts the first sentence from a plain text help text
function [text, status] = first_sentence_plain_text (help_text, max_len)
## Extract first line by searching for a period followed by a space class
## character (to support periods in numbers or words) ...
period_idx = regexp (help_text, '\.\s', "once");
## ... or a double end-of-line (we subtract 1 because we are not interested
## in capturing the first newline).
line_end_idx = regexp (help_text, "\n\n", "once") - 1;
text = help_text (1:min ([period_idx; line_end_idx; max_len; length(help_text)]));
status = 0;
endfunction
## This function extracts the first sentence from a Texinfo help text.
## The function works by removing @def* from the texinfo text. After this, we
## render the text to plain text using makeinfo, and then extract the first line.
function [text, status] = first_sentence_texinfo (help_text, max_len)
## Lines ending with "@\n" are continuation lines, so they should be
## concatenated with the following line.
help_text = strrep (help_text, "@\n", " ");
## Find, and remove, lines that start with @def. This should remove things
## such as @deftypefn, @deftypefnx, @defvar, etc.
keep = true (size (help_text));
def_idx = strfind (help_text, "@def");
if (! isempty (def_idx))
endl_idx = find (help_text == "\n");
for k = 1:length (def_idx)
endl = endl_idx(find (endl_idx > def_idx(k), 1));
if (isempty (endl))
endl = numel (keep);
endif
keep(def_idx(k):endl) = false;
endfor
## Remove the @end ... that corresponds to the @def we removed above
def1 = def_idx(1);
space_idx = find (help_text == " ");
space_idx = space_idx (find (space_idx > def1, 1));
bracket_idx = find (help_text == "{" | help_text == "}");
bracket_idx = bracket_idx (find (bracket_idx > def1, 1));
if (isempty (space_idx) && isempty (bracket_idx))
error ("get_first_help_sentence: couldn't parse texinfo");
endif
sep_idx = min (space_idx, bracket_idx);
def_type = help_text(def1+1:sep_idx-1);
end_idx = strfind (help_text, sprintf ("@end %s", def_type));
if (isempty (end_idx))
error ("get_first_help_sentence: couldn't parse texinfo");
endif
keep(end_idx(1):end) = false;
help_text = help_text(keep);
endif
## Run makeinfo to generate plain text
[help_text, status] = __makeinfo__ (help_text, "plain text");
## Extract first line with plain text method.
text = first_sentence_plain_text (help_text, max_len);
endfunction
## This function extracts the first sentence from a html help text.
## The function simply removes the tags and treats the text as plain text.
function [text, status] = first_sentence_html (help_text, max_len)
## Strip tags
[help_text, status] = strip_html_tags (help_text);
## Extract first line with plain text method.
text = first_sentence_plain_text (help_text, max_len);
endfunction
%!assert (get_first_help_sentence ('get_first_help_sentence'), ...
%! "Return the first sentence of a function's help text.")
%% Test input validation
%!error get_first_help_sentence ()
%!error get_first_help_sentence (1, 2, 3)
%!error <NAME must be a string> get_first_help_sentence (1)
%!error <MAX_LEN must be positive integer> get_first_help_sentence ("ls", "a")
%!error <MAX_LEN must be positive integer> get_first_help_sentence ("ls", 0)
%!error <MAX_LEN must be positive integer> get_first_help_sentence ("ls", 80.1)
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