## 1. Becoming error when calculate between SI one and its scaled variation

For example, conversion between meter and kilometer is not self‐evident in F#.

For help type #help;;
> open Microsoft.FSharp.Data.UnitSystems.SI.UnitSymbols;;
> let a = 195<m>;;
val a : int<m> = 195
> [<Measure>] type km;;
[<Measure>]
type km
> let b = 42<km>;;
val b : int<km> = 42
> a + b;;
a + b;;
----^
stdin(5,5): error FS0001: The unit of measure 'km' does not match the unit of measure 'm'

In this case, we must create some functions to convert these.

## 2. Becoming error when calculate with non-SI one

For example, conversion between meter and mile is not self‐evident in F#.

For help type #help;;
> open Microsoft.FSharp.Data.UnitSystems.SI.UnitSymbols;;
> let a = 10<m>;;
val a : int<m> = 10
> [<Measure>] type mile;;
[<Measure>]
type mile
> let b = 9<mile>;;
val b : int<mile> = 9
> a + b;;
a + b;;
----^
stdin(5,5): error FS0001: The unit of measure 'mile' does not match the unit of measure 'm'

In this case too, we must create some functions to convert these.

## 3. Cannot instantiate collection of units values with range notation

Surprisingly, F# cannot allow to instantiate collection of units values with range notation.

For help type #help;;
> open Microsoft.FSharp.Data.UnitSystems.SI.UnitSymbols;;
> seq {1<g>..10<g>};;
seq {1<g>..10<g>};;
-----^^^^^
stdin(7,6): error FS0001: The type 'int<g>' does not match the type 'int'

In this case, we must do the redundant operation like below:

> seq { for i in [1..10] -> i * 1<g> };;
val it : seq<int<g>> = seq [1; 2; 3; 4; ...]