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goldfirere / units

The home of the units Haskell package
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unit TH: ability to parse dimensionless units. #28

Closed nushio3 closed 10 years ago

nushio3 commented 10 years ago

I'd like our unit TH to be able to parse dimensionless units. And I think dimensionless unit should allow spaces like [si| |] , since the behavior is consistent with allowing extra spaces among unit symbol and numbers.

nushio3 commented 10 years ago

Dear @goldfirere , I'd wait your opinion rather than directly merging this.

goldfirere commented 10 years ago

I think adding support for dimensionless annotations is a good idea, but I think a different syntax is better: use 1 to indicate dimensionless. This would also allow things like [si| 1/s |] instead of [si| s^-1 |]. (Currently, the former fails to parse.) It also conforms to F#'s syntax, which was my inspiration for the syntax in the current parser. (The key not-totally-obvious thing from F# is that * and / have the same precedence, while juxtaposition binds tighter than either.)

nushio3 commented 10 years ago

I like the idea of using 1 for dimensionless unit, especially I like how it allows reciprocal units! We can also save [si| <spaces> |] as alternative form of dimensionless unit, too. Allowing both expression will contribute to decrease the surprise, when different people try to express units in different ways. And as far as I can foresee there will be no ambiguity raised by allowing both.