<ft_us>2 not parseable; <ft_us>^2 is parsable

[seanmreidy]

Hello,

I am using the SimpleUnitFormat class using the ASCII flavor. Using the parse method, I get an error when trying to do an exponent operation that should be allowed using the UCUM standard - <ft_us>2. "The exponent is an integer number and is written immediately behind the unit term."

Here's the stack trace I get:

javax.measure.format.MeasurementParseException: unexpected token INTEGER
        at app//tech.units.indriya.format.SimpleUnitFormat$DefaultFormat.parseProductUnit(SimpleUnitFormat.java:778)
        at app//tech.units.indriya.format.SimpleUnitFormat.parseObject(SimpleUnitFormat.java:332)
        at app//tech.units.indriya.format.SimpleUnitFormat$DefaultFormat.parse(SimpleUnitFormat.java:1028)
        at app//tech.units.indriya.format.SimpleUnitFormat$DefaultFormat.parse(SimpleUnitFormat.java:1023)
        at app//tech.units.indriya.format.SimpleUnitFormat$DefaultFormat.parse(SimpleUnitFormat.java:1019)

However, '<ft_us>^2' does work.

Can you let us know if the standard UCUM exponent format is supported, or if the above error is expected?

[keilw]

Sorry for the delay, did you try systems-ucum on top of Indriya? That contains a UCUMFormat implementation which supports the UCUM standard.
In SimpleUnitFormat this is expected.

[keilw]

Also could you please point out, where "<ft_us>2" is in the UCUM standard? AFAIK the notion is "[ft_us]2" and that works with UCUMFormat, but "<ft_us>2" is not recognized.

[seanmreidy]

Thanks for getting back! Few follow-ups:

1. How exactly would you recommend implementing systems-ucum? Right now we use your parse method. Would you just use UCUMFormat's parse instead of SimpleUnitFormat's? Link
2. Clarifying on your question - yes, I did mean [ft_us]2. Does that work as a direct input to Indriya? Our code has a pre-processor which converts all [/] to </>, so I put it in those terms.

[keilw]

Thanks for the quick reply. [ft_us]2 is parseable with UCUMFormat from the UCUM system.

You won't be able to parse 'ft_us^2' because there's currently no alias for that, but you can parse "ft^2" as long as the USCustomary system (also in uom-systems) was loaded.

[seanmreidy]

Thanks. Do you have guidance on when to use the UCUMFormat wrapper and when to use Indirya's SimpleUnitFormat directly? Is there any valid case to use the latter?

[keilw]

It's best to use UCUMFormat for all units defined in the UCUM system. For most other units and systems you can use SimpleUnitFormat, or as an alternative EBNFUnitFormat (using an Extended Backus-Naur Form, with mechanisms a bit similar to UCUMFormat)
In fact, all UCUM units are also registered with these, but they will display them as good as it gets using mathematical formulas, and not the UCUM standard. So if you need to use the UCUM standard, please use the system and format of that module, otherwise (or if you need to e.g. combine multiple systems) the formats of Indriya.

[seanmreidy]

Thanks, I think this give me enough info for now!