added make-mprocs function

flake.nix

@@ -14,14 +14,14 @@
     {
       writePythonApplication = {name, contentFile, extraRuntimeInputs ? [], python ? null}: 
           let
-            python-to-use = python == null then pkgs.python311 else python;
+            python-to-use = if python == null then pkgs.python311 else python;
             wrappedScript = pkgs.writeText "wrappedScript" (builtins.readFile contentFile);
           in
             pkgs.writeShellApplication {
               name = name;
               runtimeInputs = [
                   wrappedScript
-                  if python-to-use] ++ extraRuntimeInputs;
+                  python-to-use] ++ extraRuntimeInputs;
               text = ''
                   exec ${python-to-use}/bin/python ${wrappedScript} "$@"
               '';
@@ -39,5 +39,19 @@
                 exec ${pkgs.babashka}/bin/bb ${wrappedScript} "$@"
             '';
             };
+        make-mprocs = {name, derivations ? []}: let
+            mk-mprocs-procs = ret: derivation: ret ++ [{name = derivation.name;
+                                                        value = {cmd = ["${derivation}/bin/${derivation.name}"];};
+                                                        }];
+            mprocs-procs = builtins.listToAttrs (builtins.foldl' mk-mprocs-procs [] derivations);
+            mprocs-config = builtins.toJSON {procs = mprocs-procs;};
+            mprocs-config-file = pkgs.writeText "config.yaml" mprocs-config;
+          in pkgs.writeShellApplication {
+            name = name;
+            runtimeInputs = [pkgs.mprocs] ++ derivations;
+            text = ''
+                  ${pkgs.mprocs}/bin/mprocs --config ${mprocs-config-file}
+            '';
+        };
     });
 }