Simplee.IO 1.0.2

Koio |> Simple.IO

Library Simplee.IO v1.0.1 implements common IO functionality used by all other Simple projects. The namespace of the library is Simplee.IO.

    open Simplee.IO

Here is the main functionality exposed:

1. Stack free monad

1. Stack

1.1 The Free Monad

The library exposes a free monad for stack operations. The stack monad comes with 3 instructions:

1. push instruction which pushes a value on top of the stack
2. pop instruction which extracts the value from the top of the stack
3. peek instruction which returns the value from the top of the stack without removing it from the stack.

The instructions use the error type provided in Simplee.Common package in order to return the evantual failures.

1.2 Computation Builder

This monad is wrapped within stk, a computation expression builder.

The user can construct flows into an imperative way using this builder.

    let flow = stk {
        let! _ = stkpush 10
        let! _ = stkpeek ()
        let! r = stkpop ()
        return r
        }

1.3 Built-in Interpreters

The flows generated with the builder can be interpreted using built-in interpretors. The library provides two interpretors:

1. stklstr - an interpretor that transfors a flow of instructions into a listing.
2. stkim - an interpretor that implements an in-memory stack which can have or not an upper limit.

Here is an example for the stack lister:

    flow
    |> stklst (fun () -> 10)
    |> List.iter (lstrln2str >> printfn "%s")

And here is an example for the in-memory stack:

    flow
    |> stkimrun (stkimEU ())        // start with an empty stack, without upper limit
    |> fst
    |> printfn "Stack: %O"

There are several convenience function which can create an in-memory stack: stkimEU, stkimE, stkimA where you can set the upper limit of the stack and/or the initial values in the stack.

1.4 User-defined Interpreters

A user can implement its own interpreter (eg. the stack is implemented on a database). The user will have to implement push, pop, peek, and pur functions, which stand for each of the stack instructions and for the function that return the final result of the workflow.

One of the arguments for these functions is the state instance which can be used to pass and or reuse information from one instruction to the next one. For example this state is the in-memory list of values for the in-memory interpreter. In the case of the lister, the state is the current line in the listing and the collection of listing lines accumulated so far.

Here is an example of the implementation for the push function:

    let private push (SLister (ln, _, _) as s) v =

        (ln, "psh", v |> sprintf "%A")
        |> SLstrLn
        |> lstappnd s,

        () |> Ok

2. Installation

You can install the Simplee.IO nuget package by using one of the following commands:

PM> Install-Package Simplee.IO -Version 1.0.0
> dotnet add package Simplee.IO --version 1.0.0 
> paket add Simplee.IO --version 1.0.0