Harvey, > http://rain.aos.wisc.edu/%7Egpetty/physunits.html > http://xml.coverpages.org/OlkenMeasurementUnitsSyntax.html > http://en.wikipedia.org/wiki/Level_of_measurement Thanks for the references. It looks like Fortran-95 can do some pretty cool stuff. > Petty's paper explains the idea of non-integer powers of base-units. > Note that I am NOT suggesting allowing unit strings with non-integer > powers. I assume they are useful only during calculation, not for > input/output. Thus ut_format could simply round powers to the nearest > integer. Like I sand in my previous reply, I'd rather restrict argument to integers where appropriate. > One feature of udunits-1 which I disliked was the merging of the Julian > and Gregorian calendars (with a specific calendar change date). The > date of conversion varied from country to country. In fact some > countries (e.g. Russia) did not change to Gregorian until the 20th > century. Gregorian dates should be treated as a separate unit from > Julian dates and it should be possible to convert from one to the other. > I note your comment in the manual about now having second thoughts about > the wisdom of supporting dates at all. Yup. I hate the time-offset unit. I should never have created it. Anyone who uses it as a replacement for a full calendaring system (which is what people try to do) has rocks for brains. The only solution would be to implement a full calendaring subsystem with the UDUNITS package, and I'm just not willing to expend that much effort on so little a benefit. > Note Olken's distinction between 'measures' and 'coordinates'. Udunits > has the concept of a time-origin (often related to dates), but this > 'coordinate' concept is relevant to non-time dimensions. E.g. eastings > and northings are relative to an origin. Note that it is legal to > divide one measure by another, but not one coordinate by another. In > other words (see wikipedia URL above) a measure is an 'ratio > measurement' while a coordinate is an 'interval measurement'. I'm not > sure what all this means for udunits but maybe any unit could have an > origin. Most units can be made relative to an origin via the ut_offset() function. Regards, Steve Emmerson Ticket Details =================== Ticket ID: ONU-754617 Department: Support UDUNITS Priority: Normal Status: On Hold
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