Re: Isnumeric function? - Mailing list pgsql-sql

How about this

CREATE OR REPLACE FUNCTION is_numeric ( text ) RETURNS bool AS ' if { [string is integer $1] || [string is double $1] }
{  return true } return false
 
' LANGUAGE 'pltcl' IMMUTABLE;


SELECT is_numeric ( '-1' );is_numeric
------------t
(1 row)

SELECT is_numeric ( '+1e-1' );is_numeric
------------t
(1 row)

SELECT is_numeric ( '1.1.1' );is_numeric
------------f
(1 row)

-- 
Vadim Passynkov


-----Original Message-----
From: Jeff Eckermann [mailto:jeff_eckermann@yahoo.com]
Sent: Thursday, September 09, 2004 10:02 AM
To: Thomas Swan; olly@lfix.co.uk
Cc: Josh Berkus; Theo Galanakis; pgsql-sql@postgresql.org
Subject: Re: [SQL] Isnumeric function?


Ok, how about this.  At least it works in my testing. 
I have extended it to allow a negative sign (trailing
also), which I would expect to be allowed in a
comprehensive "isnumeric" function.  If I am wrong,
feel free to slap me around; although correcting the
regex would be more constructive. ;-)

create function isnumeric(text) returns boolean as '
select $1 ~
\'(-?([0-9]+\\.?[0-9]*|[0-9]*\\.?[0-9]+)|([0-9]+\\.?[0-9]*|[0-9]*\\.?[0-9]+)
-?)\'
'language 'sql';

--- Thomas Swan <tswan@idigx.com> wrote:

> Oliver Elphick wrote:
> 
> >On Wed, 2004-09-08 at 18:48, Josh Berkus wrote:
> >  
> >
> >>Theo, Oliver,
> >>
> >>    
> >>
> >>>Any reason why you don't like  ~
> '^([0-9]?)+\.?[0-9]*$' ?
> >>>      
> >>>
> >>Yes, because it also matches "." , which is not a
> valid numeric value.
> >>
> >>    
> >>
> >>> ~ '^([0-9]+|[0-9]+\\.[0-9]*|[0-9]*\\.[0-9]+)$'
> >>>      
> >>>
> >>Ah, the brute force approach ;-)
> >>    
> >>
> >
> >Nothing like using a nice big hammer!
> >
> >  
> >
> Would "^([0-9]+\\.{0,1}[0-9]*|\\.[0-9]+)$" be a
> little cleaner?
> 
> >>Actually, the above could be written:
> >>
> >>~ '^([0-9]+)|([0-9]*\\.[0-9]+)$'
> >>    
> >>
> >
> >But that doesn't allow a trailing decimal point.
> >
> >  
> >
> >>... though that still seems inelegant to me.  Is
> there a regex expert in the 
> >>house?
> >>    
> >>
> >
> >All the elegant approaches I can think of match the
> empty string. There
> >must be at least one digit and 0 or 1 decimal point
> with no other
> >characters permitted.  If you use this as a
> constraint, you could make
> >it elegant and combine it with another constraint
> to exclude '' and '.'.
> >  
> >
> 
> 
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