F# Units of measure - 'lifting' values to float

Question

When importing numbers from a csv file, I need to convert them to floats with unit.

Currently I do this with an inline function:

data |> List.map float |> List.map (fun n -> n * 1.0<m>)

But I'm wondering if there is a more elegant way to do this - or do I have to create my own 'units' module with conversion functions?

What would be really nice would be something like this, but I doubt it's possible...

data |> List.map float |> List.map lift<m>

This is the opposite of my previous question (How to generically remove F# Units of measure).

UPDATE: For homemade units, I've tried this, which works ok:

[<Measure>]
type km = 
    static member lift (v:float) = v * 1.0<km>

data |> List.map float |> List.map km.lift

or, following the question in this answer

data |> List.map (float >> km.lift)

score 2 · Accepted Answer · edited Feb 11 '10 at 16:24

2

It looks like units of measure can't be type parameters for the moment (no idea if this will change). So the shortest way to write this is:

data |> List.map float |> List.map ((*) 1.0<m>)

EDIT

See also now FloatWithMeasure here

edited Feb 11 '10 at 16:24

Brian

answered Jan 07 '09 at 09:58

Robert

Given that units are purely compile-time, it doesn't seem likely to change. – Alexey Romanov Jan 07 '09 at 15:04
FloatWithMeasure just saved me from a lot of hair pulling, thanks :) – Ed Ayers Dec 18 '11 at 14:08

score 1 · Answer 2 · answered Jan 08 '09 at 12:49

1

Is there any reason why you have to map twice? What's wrong with this:

data |> List.map (fun x -> (float x) * 1.0<m>)

answered Jan 08 '09 at 12:49

Juliet

Yeah, I could, have done so, but the idea was that my lift function would be generally applicable to floats. But see corrected code in UPDATE in question. – Benjol Jan 09 '09 at 10:04

2 Answers2