Thread: "format" function documentation fix
(Please CC me the reply, since I'm not subscribed to the list.) Hi, The last example from http://www.postgresql.org/docs/9.3/static/functions-string.html#FUNCTIONS-STRING-FORMAT - "examples using width fields and the - flag" seems to be incorrect, see the attached patch. Regards, r.
Attachment
On 14 September 2013 09:29, rudolf <stu3.1@eq.cz> wrote: > (Please CC me the reply, since I'm not subscribed to the list.) > > Hi, > > The last example from > http://www.postgresql.org/docs/9.3/static/functions-string.html#FUNCTIONS-STRING-FORMAT > - "examples using width fields and the - flag" seems to be incorrect, see > the attached patch. > No, the example is correct. Referring to the documentation above that: If the width argument is negative, the result is left aligned (as if the - flag had been specified) ... This applies even if the "-" flag is also specified. So the last example is meant to illustrate that 2 minuses don't make a plus here. Regards, Dean
On 17 September 2013 10:00, rudolf <stu3.1@eq.cz> wrote: > (Please CC me the reply, since I'm not subscribed to the list.) > > Dean Rasheed wrote: >> >> On 14 September 2013 09:29, rudolf <stu3.1@eq.cz> wrote: >>> >>> The last example from >>> >>> http://www.postgresql.org/docs/9.3/static/functions-string.html#FUNCTIONS-STRING-FORMAT >>> - "examples using width fields and the - flag" seems to be incorrect, see >>> the attached patch. >> >> >> No, the example is correct. Referring to the documentation above that: >> >> If the width argument is negative, the result is left aligned (as >> if the - flag had been specified) ... >> >> This applies even if the "-" flag is also specified. So the last >> example is meant to illustrate that 2 minuses don't make a plus here. > > > That's very unusual, IMO. This behavior follows some SQL standard or is it > an invention of PostgreSQL? > It's not part of the SQL standard, but it is based on C printf() and friends from the Single UNIX Specification, see for example http://pubs.opengroup.org/onlinepubs/7908799/xsh/fprintf.html My reading of that is that "-" is to be treated as a flag, not as a minus sign, so specifying it multiple times has the same effect as specifying it once. On my linux box, the following both produce left-justified output: printf("'%-10s'\n", "foo"); printf("'%--10s'\n", "foo"); Regards, Dean
(Please CC me the reply, since I'm not subscribed to the list.) Dean Rasheed wrote: > On 14 September 2013 09:29, rudolf <stu3.1@eq.cz> wrote: >> The last example from >> http://www.postgresql.org/docs/9.3/static/functions-string.html#FUNCTIONS-STRING-FORMAT >> - "examples using width fields and the - flag" seems to be incorrect, see >> the attached patch. > > No, the example is correct. Referring to the documentation above that: > > If the width argument is negative, the result is left aligned (as > if the - flag had been specified) ... > > This applies even if the "-" flag is also specified. So the last > example is meant to illustrate that 2 minuses don't make a plus here. That's very unusual, IMO. This behavior follows some SQL standard or is it an invention of PostgreSQL? Thanks, r.
hello
2013/9/17 rudolf <stu3.1@eq.cz>
(Please CC me the reply, since I'm not subscribed to the list.)
Dean Rasheed wrote:On 14 September 2013 09:29, rudolf <stu3.1@eq.cz> wrote:The last example from
http://www.postgresql.org/docs/9.3/static/functions-string.html#FUNCTIONS-STRING-FORMAT
- "examples using width fields and the - flag" seems to be incorrect, see
the attached patch.
No, the example is correct. Referring to the documentation above that:
If the width argument is negative, the result is left aligned (as
if the - flag had been specified) ...
This applies even if the "-" flag is also specified. So the last
example is meant to illustrate that 2 minuses don't make a plus here.
That's very unusual, IMO. This behavior follows some SQL standard or is it an invention of PostgreSQL?
this is postgresql feature - standard doesn't support any similar functionality - and printf is some like developer Esperanto. We significantly reduced complexity of printf function and we modified basic rules for usage in SQL, but some very typical rules - like format placeholders, we share - we don't introduce own rules there.
Regards
Pavel Stehule
Thanks,
r.
--
Sent via pgsql-docs mailing list (pgsql-docs@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-docs
(Please CC me the reply, since I'm not subscribed to the list.) Pavel Stehule wrote: > 2013/9/17 rudolf > Dean Rasheed wrote: [...] > This applies even if the "-" flag is also specified. So the last > example is meant to illustrate that 2 minuses don't make a plus > here. > > That's very unusual, IMO. This behavior follows some SQL standard or > is it an invention of PostgreSQL? > > this is postgresql feature - standard doesn't support any similar > functionality - and printf is some like developer Esperanto. We > significantly reduced complexity of printf function and we modified > basic rules for usage in SQL, but some very typical rules - like format > placeholders, we share - we don't introduce own rules there. Yes, as I already wrote to Dean (and forgot to cc the list), you are right, the behavior is correct. Thanks for the explanation! Kind regards, r.