I'm glad that some understand that I want to have strong type checking and not multiform filed (with special compound type).It strikes me that the right level of constraint is the quantity being represented: length / mass / time / velocity.
Then you could store any of: '1inch', '2m', '3km', '4light-years' in a "length" column.
Ofcourse, only one of those is in SI units :) Just like the interval type, all this could be handled by the parser. Define some costant conversions, after all a light-year is about 9.5e15 metres.
The question is, if you put one inch in, do you expect to get one inch out?
I want that whater is the unit in, the data is coherent. And the output will be format with convert function.
If I have a column with "speed DOUBLE(m1s-1)"
I want to be able to put in in any unit format.
If I want special output, I would have a function
doubleunit_to_char(speed,'si') that will output "3 m/s" and
doubleunit_to_char(speed,'si','fr') that will output "3 mètre/seconde" and
doubleunit_to_char(speed,'si','en') that will output "3 meter/second" and
doubleunit_to_char(speed,'british','en') that will output "xxx yard/day" ;-)
I am in the process of writing such function to convert from test to an internal format.
But the problem is that all the work I am doing is about coupound type (double, unit)
the unit type is an integer with for table for the definition of unit, convertion and translation in human form.
Cordialement, Jean-Gérard Pailloncy
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