Convert an interval in seconds

Hi all !

I've search all the doc to find a function which would allow me to convert an 
interval into a number of seconds. What I get is @ 1 hour, what I would like is 
-3600. I'd think to something like select interval('sec', myTime) - Ingres 
syntax - but it doesn't work.

Does somebody has an idea ?

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B. Carrupt