An API Implementing the Reader Pattern

MyApiReader.fs

type ConnectionString = CON of string
type EnvVariable = ENV of string
type RandomNum = RND of int

type MyApiContext = 
  { Dep1 : ConnectionString ; 
    Dep2 : EnvVariable;
    Dep3 : RandomNum }

type MyApiPart<'a> = Reader<MyApiContext -> 'a>

module MyApi =
    open Reader

    // MyApiPart<string>
    let function1 =
        let dostuff (CON conn) =
            "cs:" + conn + "!"
        pure (fun ctx -> dostuff ctx.Dep1)
    
    // string -> MyApiPart<int>
    let function2 (s:string) =
        let dostuff (ENV env) (RND random) =
            if random % 2 = 0 then Some random else None
        pure (fun ctx -> match dostuff ctx.Dep2 ctx.Dep3 with
                         | Some random -> random
                         | None        -> s.Length )
    
    // int -> MyApiPart<string>
    let function3 (i: int) =
        let dostuff (ENV env) =
            "env:" + env + "i:" + (string i) + "!"
        pure (fun ctx -> dostuff ctx.Dep2)
    
    // string -> int
    let function4 (s: string) =
        let dostuff = s.Length
        dostuff