convert text to number or number to text - Mailing list pgsql-sql

I'm trying to do an update query that compares an int4 field to a variable 
which I think contains a string (it was passed in through cgi.pm).  can I 
convert that string to an integer? - it will always be a number passing 
through.  I vaguely remember oracle having a to_number function - does 
postgres have something similar?

jt