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

From: Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Re: proposal: a width specification for s specifier (format function), fix behave when positional and ordered placeholders are used
Date: 2013-01-29 08:19:39
Message-ID: CAEZATCWYncqOjAuGYz-DCJjpZdjbbCViyvPfG0uTBp-EHM4K_A@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
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


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