Pinned agda version to 2.6.4.3. (#22)

* Pinned agda version to 2.6.4.3.
* Added agda instructions to read-me file.

Fixes #21

README.md

@@ -23,6 +23,24 @@ More documentation about Leios can be found in the [web site](https://leios.card
 * [leios-sim](leios-sim) contains experimental code to simulate the Leios protocol
 * [site](site) contains the sources of the aforementioned web site
 
+## Specification
+
+Build the Agda specification for Leios using either
+
+```console
+$ nix build --no-link --accept-flake-config .#leiosSpec
+```
+
+or
+
+```console
+$ nix develop
+
+$ cd formal-spec
+
+$ agda Leios/SimpleSpec.agda
+```
+
 ## Archive
 
 The [Leios CIP](https://github.com/cardano-foundation/CIPs/pull/379)

flake.nix

@@ -1,34 +1,18 @@
-# Docs for this file: https://github.com/input-output-hk/iogx/blob/main/doc/api.md#flakenix
 {
-  description = "Change the description field in your flake.nix";
+  description = "Ouroboros Leios";
 
 
   inputs = {
     iogx = {
       url = "github:input-output-hk/iogx";
     };
 
-    # nixpkgs.follows = "haskell-nix/nixpkgs";
-
-    # hackage = {
-    #   url = "github:input-output-hk/hackage.nix";
-    #   flake = false;
-    # };
-
-    # CHaP = {
-    #   url = "github:input-output-hk/cardano-haskell-packages?ref=repo";
-    #   flake = false;
-    # };
-
-    # haskell-nix = {
-    #   url = "github:input-output-hk/haskell.nix";
-    #   inputs.hackage.follows = "hackage";
-    # };
+    # Agda version 2.6.4.3
+    agda-nixpkgs.url = "github:NixOS/nixpkgs?ref=4284c2b73c8bce4b46a6adf23e16d9e2ec8da4bb";
 
   };
 
 
-  # Docs for mkFlake: https://github.com/input-output-hk/iogx/blob/main/doc/api.md#mkflake
   outputs = inputs: inputs.iogx.lib.mkFlake {
 
     inherit inputs;

nix/agda.nix

@@ -10,7 +10,7 @@ let
                      else "";
   };
 
-  customAgda = pkgs;
+  customAgda = inputs.agda-nixpkgs.legacyPackages;
 
   agdaStdlib = customAgda.agdaPackages.standard-library;