Greg Stark <stark@mit.edu> writes:
> On 24 January 2017 at 03:42, Peter van Hardenberg <pvh@pvh.ca> wrote:
>> The basic concept is that the value of a currency type is that it would
>> allow you to operate in multiple currencies without accidentally adding
>> them. You'd flatten them to a single type if when and how you wanted for any
>> given operation but could work without fear of losing information.
> I don't think this even needs to be tied to currencies. I've often
> thought this would be generally useful for any value with units.
There already is an extension somewhere for attaching units to numeric
values, which would be a place to start from for this purpose. The
things I think are unique to the currency situation are:
* Time-varying conversion ratios.
* Conventional number of decimal places for any given currency.
* Idiosyncratic I/O formats (symbol to left or right of number,
odd rules for negatives, etc). I think the space here is covered
by the POSIX currency locale rules.
regards, tom lane