Start implementing the Epichord DHT: NodeID type

src/EpiChord.hs

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+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{- |
+Module      : EpiChord
+Description : An opinionated implementation of the EpiChord DHT by Leong et al.
+Copyright   : (c) schmittlauch, 2019
+License     : AGPL-3
+Stability   : experimental
+
+Here be dragons
+-}
+
+module EpiChord where
+
+newtype NodeID = NodeID { getNodeID :: Integer } deriving (Eq, Show, Enum)
+
+instance Bounded NodeID where
+    minBound = NodeID 0
+    maxBound = NodeID (2^idBits - 1)
+
+instance Num NodeID where
+    a + b = NodeID $ (getNodeID a + getNodeID b) `mod` (getNodeID maxBound + 1)
+    a * b = NodeID $ (getNodeID a * getNodeID b) `mod` (getNodeID maxBound + 1)
+    a - b = NodeID $ (getNodeID a - getNodeID b) `mod` (getNodeID maxBound + 1)
+    -- Todo: decide whether throwing exceptions isn't better
+    fromInteger i = NodeID $ i `mod` (getNodeID maxBound + 1)
+    signum = NodeID . signum . getNodeID
+    abs = NodeID . abs . getNodeID  -- ToDo: make sure that at creation time only IDs within the range are used
+
+-- Todo: Num Instanz selbst definieren
+-- Todo: Ist es sinnvoll, das hier Teil von Ord zu machen?
+
+-- define protocol constants
+idBits :: Integer
+idBits = 256

src/shell.nix

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+let
+  pkgs = import <nixpkgs> {};
+in
+pkgs.mkShell {
+  buildInputs = [
+    (pkgs.haskellPackages.ghcWithPackages (pkgs: with pkgs;
+      [
+        mtl
+      ]))
+  ];
+}