Mercurial > hg > octave-nkf
changeset 13297:42d5ff896e85
substr.m: Expand function to accept negative values for length argument.
* substr.m: Expand function to accept negative values for length argument.
Improve input validation and add more tests. Update docstring.
author | Rik <octave@nomad.inbox5.com> |
---|---|
date | Sat, 08 Oct 2011 11:08:50 -0700 |
parents | 27da11c63d98 |
children | 86d18a3cc911 |
files | scripts/strings/substr.m |
diffstat | 1 files changed, 63 insertions(+), 30 deletions(-) [+] |
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line diff
--- a/scripts/strings/substr.m +++ b/scripts/strings/substr.m @@ -17,25 +17,32 @@ ## <http://www.gnu.org/licenses/>. ## -*- texinfo -*- -## @deftypefn {Function File} {} substr (@var{s}, @var{offset}, @var{len}) +## @deftypefn {Function File} {} substr (@var{s}, @var{offset}) +## @deftypefnx {Function File} {} substr (@var{s}, @var{offset}, @var{len}) ## Return the substring of @var{s} which starts at character number ## @var{offset} and is @var{len} characters long. ## -## If @var{offset} is negative, extraction starts that far from the end of -## the string. If @var{len} is omitted, the substring extends to the end -## of S. +## Position numbering for offsets begins with 1. If @var{offset} is negative, +## extraction starts that far from the end of the string. +## +## If @var{len} is omitted, the substring extends to the end of @var{S}. A +## negative value for @var{len} extracts to within @var{len} characters of +## the end of the string ## -## For example: +## Examples: ## ## @example ## @group ## substr ("This is a test string", 6, 9) ## @result{} "is a test" +## substr ("This is a test string", -11) +## @result{} "test string" +## substr ("This is a test string", -11, -7) +## @result{} "test" ## @end group ## @end example ## -## This function is patterned after AWK@. You can get the same result by -## @code{@var{s}(@var{offset} : (@var{offset} + @var{len} - 1))}. +## This function is patterned after the equivalent function in Perl. ## @end deftypefn ## Author: Kurt Hornik <Kurt.Hornik@wu-wien.ac.at> @@ -47,34 +54,60 @@ print_usage (); endif - if (ischar (s)) - nc = columns (s); - if (abs (offset) > 0 && abs (offset) <= nc) - if (offset <= 0) - offset += nc + 1; - endif - if (nargin == 2) - eos = nc; - else - eos = offset + len - 1; - endif - if (eos <= nc) - t = s (:, offset:eos); - else - error ("substr: length = %d out of range", len); - endif + if (! ischar (s)) + error ("substr: S must be a string or string array"); + elseif (! isscalar (offset) || (nargin == 3 && ! isscalar (len))) + error ("substr: OFFSET and LEN must be scalar integers"); + endif + + offset = fix (offset); + nc = columns (s); + if (abs (offset) > nc || offset == 0) + error ("substr: OFFSET = %d out of range", offset); + endif + + if (offset <= 0) + offset += nc + 1; + endif + + if (nargin == 2) + eos = nc; + else + len = fix (len); + if (len < 0) + eos = nc + len; else - error ("substr: OFFSET = %d out of range", offset); + eos = offset + len - 1; endif - else - error ("substr: expecting string argument"); endif + if (eos > nc) + error ("substr: length LEN = %d out of range", len); + elseif (offset > eos && len != 0) + error ("substr: No overlap with chosen values of OFFSET and LEN"); + endif + + t = s(:, offset:eos); + endfunction -%!assert(strcmp (substr ("This is a test string", 6, 9), "is a test")); + +%!assert (substr ("This is a test string", 6, 9), "is a test"); +%!assert (substr ("This is a test string", -11), "test string"); +%!assert (substr ("This is a test string", -11, 4), "test"); +%!assert (substr ("This is a test string", -11, -7), "test"); +%!assert (substr ("This is a test string", 1, -7), "This is a test"); +%!assert (substr ("This is a test string", 1, 0), ""); -%!error substr (); +%% Test input validation +%!error substr () +%!error substr ("foo", 2, 3, 4) +%!error substr (ones (5, 1), 1, 1) +%!error substr ("foo", ones(2,2)) +%!error substr ("foo", 1, ones(2,2)) +%!error substr ("foo", 0) +%!error substr ("foo", 5) +%!error substr ("foo", 1, 5) +%!error substr ("foo", -1, 5) +%!error substr ("foo", 2, -5) -%!error substr ("foo", 2, 3, 4); -