On Mon, Mar 07, 2011 at 02:08:10PM -0800, bricklen wrote: > On Mon, Mar 7, 2011 at 1:20 PM, Piotr Czekalski <pczekal...@techbaza.pl> > wrote: > > Hello pgsql community, > > > > Is there any string function (other than regex / scan & compare loop) to > > obtain a list (or even a count) of characters within a string? > > strpos and position seems to return only first occurence of a char/string > > within substring. > > The goal is to check if a string contains equal number of opening and > > closing parenthesis, and if there are any of them. > > > > Regards, > > > > Piotr Czekalski > > Couple examples here that might help to get you started > http://www.postgres.cz/index.php/PostgreSQL_SQL_Tricks#Get_count_of_substrings_in_string
Oh, I like that trick! A little substitution and rearranging leads to: CREATE OR REPLACE FUNCTION balanced_parens(text) RETURNS integer AS $$ SELECT(length(replace($1, '(', '')) - length(replace($1,')',''))) ; $$ LANGUAGE SQL IMMUTABLE; Generalizing (curly braces? brackets?) CREATE OR REPLACE FUNCTION balanced_pairs(text,text,text) RETURNS integer AS $$ SELECT(length(replace($1, $2, '')) - length(replace($1,$3,''))) ; $$ LANGUAGE SQL IMMUTABLE; Ross -- Ross Reedstrom, Ph.D. reeds...@rice.edu Systems Engineer & Admin, Research Scientist phone: 713-348-6166 Connexions http://cnx.org fax: 713-348-3665 Rice University MS-375, Houston, TX 77005 GPG Key fingerprint = F023 82C8 9B0E 2CC6 0D8E F888 D3AE 810E 88F0 BEDE -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql