[question] How best to obtain numerical value from a dimensionless quantity?

[eriknstevenson]

Hello,

First of all, thanks for the work you have put into this library, I have found it to be quite useful in my project. Just hoping to get some clarification on what is the best way to obtain a numerical value from a dimensionless quantity.

The documentation is clear for cases in which the value has a unit:

v :: Velocity Prelude.Double
v = 90 *~ (kilo meter / hour)
numval :: Prelude.Double
numval = v /~ (meter / second)

However, for cases such as the following:

v2 :: Velocity Prelude.Double
v2 = 150 *~ (kilo meter / hour)
vratio :: Dimensionless Double
vratio = v / v2

I am unsure of what unit to divide by here to obtain the double on its own.

I have currently resorted to the following:

numvratio :: Double
numvratio = (v /~ (kilo meter / hour)) Prelude./ (v2 /~ (kilo meter / hour))

Just wondering if there might be a nicer way to do this, and I apologize if I have missed something obvious in the documentation.

Thanks!

[bjornbm]

Hi Erik, just use the unit one! :)

On 5 May 2018, at 17:03, Erik Stevenson notifications@github.com wrote:

Hello,

First of all, thanks for the work you have put into this library, I have found it to be quite useful in my project. Just hoping to get some clarification on what is the best way to obtain a numerical value from a dimensionless quantity.

The documentation is clear for cases in which the value has a unit:

v :: Velocity Prelude.Double v = 90 *~ (kilo meter / hour) numval :: Prelude.Double numval = v /~ (meter / second) However, for cases such as the following:

v2 :: Velocity Prelude.Double v2 = 150 *~ (kilo meter / hour) vratio :: Dimensionless Double vratio = v / v2 I am unsure of what unit to divide by here to obtain the double on its own.

I have currently resorted to the following:

numvratio :: Double numvratio = (v /~ (kilo meter / hour)) Prelude./ (v2 /~ (kilo meter / hour)) Just wondering if there might be a nicer way to do this, and I apologize if I have missed something obvious in the documentation.

Thanks!

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[eriknstevenson]

Perfect! Thank you.

[dmcclean]

If you have suggestions as to how to improve the examples to make this more clear, they would be appreciated.