Re: Re: proposal: a width specification for s specifier (format function), fix behave when positional and ordered placeholders are used

On 28 January 2013 20:32, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> wrote:
> In general a format specifier looks like:
>
> %[parameter][flags][width][.precision][length]type
>

This highlights another problem with the current implementation ---
the '-' flag and the width field need to be parsed separately. So
'%-3s' should be parsed as a '-' flag followed by a width of 3, not as
a width of -3, which is then interpreted as left-aligned. This might
seem like nitpicking, but actually it is important:

* In the future we might support more flags, and they can be specified
in any order, so the '-' flag won't necessarily come immediately
before the width.

* The width field is optional, even if the '-' flag is specified. So
'%-s' is perfectly legal and should be interpreted as '%s'. The
current implementation treats it as a width of 0, which is wrong.

* The width field might not be a number, it might be something like *
or *3$. Note that the SUS allows a negative width to be passed in as a
function argument using this syntax, in which case it should be
treated as if the '-' flag were specified.

Regards,
Dean