Creating a 'SET' type

Hi,

I am trying to emulate MySQL's SET type, by creating a new postgresql type.

However, is it possible to create a type that has different parameters
wherever it is used.

For instance - the varchar type takes as a parameter the max characters in
the field.  Although there is only one varchar type, it has different
properties depending on whether or not it is varchar(5) or varchar(20).

I wish to be able to declare:

bitset('LOW','MEDIUM','HIGH')  // Not sure of exact syntax

Internally stored as an int4.

The trouble is in writing the in and out functions.  They need to be able to
store a list of token names in order to recreate the comma delimited list of
tokens from the internal bitset, and vice versa...

Any help?

Thanks,

Chris

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Christopher Kings-Lynne
Family Health Network (ACN 089 639 243)