add Fault monad

nib/default.nix

@@ -1,12 +1,17 @@
 {systems, ...}: let
+  mergeAttrsList = std.attrs.mergeAttrsList;
+
   std = import ./std {};
-  parse = import ./parse {
+  stdSubMods = {
     attrs = std.attrs;
+    fault = std.fault;
     lists = std.lists;
     result = std.result;
   };
+
+  parse = import ./parse (mergeAttrsList [stdSubMods]);
 in
-  std.attrs.mergeAttrsList [
+  mergeAttrsList [
     # submodule content is accessible first by submodule name
     # then by the name of the content (ie self.submodule.myFunc)
     {inherit parse;}

nib/std/default.nix

@@ -1,5 +1,6 @@
 {...}: let
   attrs = import ./attrs.nix {inherit lists;};
+  fault = import ./fault.nix {};
   lists = import ./lists.nix {};
   result = import ./result.nix {inherit lists;};
 in
@@ -8,5 +9,5 @@ in
 
     # submodule content is accessible first by submodule name
     # then by the name of the content (ie self.submodule.myFunc)
-    {inherit attrs lists result;}
+    {inherit attrs fault lists result;}
   ]

nib/std/fault.nix

@@ -0,0 +1,16 @@
+{...}: rec {
+  # Fault Monad
+  # Wrapper around an error (ie builtins.abort)
+  Fault = error: {
+    error = error;
+  };
+
+  # Pattern Matching
+  isFault = F: builtins.attrNames F == ["error"];
+
+  # Unwrap (Monadic Return Operation)
+  unwrap = F: F.error;
+
+  # Map (Monadic Bind Operation)
+  map = f: F: Fault (f (unwrap F));
+}