`type t =`

1. `| Zero`
   (*

   For 0, unit is optional

   *)
2. `| Em of float`
   (*

   Relative to the font size

   *)
3. `| Ex of float`
   (*

   Relative to the x-height

   *)
4. `| Px of float`
   (*

   Relative to the viewing device

   *)
5. `| Gd of float`
   (*

   Relative to the grid

   *)
6. `| Rem of float`
   (*

   Relative to the font size of the root

   *)
7. `| Vw of float`
   (*

   Relative to the viewport's width

   *)
8. `| Vh of float`
   (*

   Relative to the viewport's height

   *)
9. `| Vm of float`
   (*

   Relative to the smallest of the viewport's width or height

   *)
10. `| Ch of float`
    (*

    Relative to the width of a char '0'

    *)
11. `| Mm of float`
    (*

    in Milimeter

    *)
12. `| Cm of float`
    (*

    in Centimeter

    *)
13. `| In of float`
    (*

    in Inch

    *)
14. `| Pt of float`
    (*

    in Points (72pt = 1in)

    *)
15. `| Pc of float`
    (*

    in Picas (1pc = 12pt)

    *)

The type of length attributes. Mdc documentation: https://developer.mozilla.org/en/CSS/length and specification: http://www.w3.org/TR/css3-values/#lengths

`type js_t = private Js.js_string Js.t`

Js representation of lengths.

Conversion functions

`val string_of_t : t -> string`
`val js : t -> js_t`
`val ml : js_t -> t`