Re: [PATCH] Supplant the "while case ... break ;; esac" idiom

Pierre Habouzit [off-list ref] writes:

On Mon, Sep 24, 2007 at 07:57:31AM +0000, David Kastrup wrote:

quoted

"David Symonds" [off-list ref] writes:

quoted

On 24/09/2007, David Kastrup [off-list ref] wrote:

quoted

Mike Hommey [off-list ref] writes:

quoted

On Sun, Sep 23, 2007 at 10:42:08PM +0200, David Kastrup wrote:

quoted

-while case $# in 0) break ;; esac
+while test $# != 0

Wouldn't -ne be better ?

Why?

Because -ne does a numeric comparison, != does a string comparison,
and it's a numeric comparison happening, semantically speaking.

I don't see the point in converting $# and 0 into numbers before
comparing them.  "!=" is quite more readable, and the old code also
compared the strings.

  Fwiw $# already is a number.

It isn't.

Hence test $# -ne 0 is definitely a better test.

/* TEST/[ builtin. */
int
test_builtin (list)
     WORD_LIST *list;
{
  char **argv;
  int argc, result;

  /* We let Matthew Bradburn and Kevin Braunsdorf's code do the
     actual test command.  So turn the list of args into an array
     of strings, since that is what their code wants. */
  if (list == 0)
    {
      if (this_command_name[0] == '[' && !this_command_name[1])
	{
	  builtin_error ("missing `]'");
	  return (EX_BADUSAGE);
	}

      return (EXECUTION_FAILURE);
    }

  argv = make_builtin_argv  (list, &argc);
  result = test_command (argc, argv);
  free ((char *)argv);

  return (result);
}

  $# != 0 would yield sth like (strcmp(sprintf("%d", argc), "0"))
  $# -ne 0 would yield sth like (argc != atoi("0")).

  Not that it matters much, but the latter looks better to me.

Not to me.  The code does not support your argument, and all $x
expansions certainly are strings, according to manual and usage.  I
will rework the patch this evening in order to get a commit message
more placable to Junio, and I will at his request remove all of the
(redundant) quoting.  But removing quoting from $# does not turn it
into a number: it remains the same string '0'.  If someone else feels
he should replace all "=" and "!=" tests for "numeric" comparisons
with the unreadable numeric tests, he can go ahead proposing a
separate patch that should not just cover $#.

You can have bash declare numeric variables, but even they are strings
(they just auto-evaluate on assignment):

declare -i nonsense
nonsense="3+$(echo 4)"
echo "$nonsense"

gives 7, even though everything has been "strings" here.

-- 
David Kastrup