XXX when did i forget to have this here?

lang/funcs/structs/util.go

@@ -0,0 +1,65 @@
+// Mgmt
+// Copyright (C) 2013-2023+ James Shubin and the project contributors
+// Written by James Shubin <[email protected]> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package structs
+
+import (
+	"github.com/purpleidea/mgmt/lang/funcs/simple"
+	"github.com/purpleidea/mgmt/lang/interfaces"
+	"github.com/purpleidea/mgmt/lang/types"
+	"github.com/purpleidea/mgmt/lang/types/full"
+)
+
+// In the following set of conversion functions, a "constant" Func is a node
+// with in-degree zero which always outputs the same function value, while a
+// "direct" Func is a node with one upstream node for each of the function's
+// arguments.
+
+func FuncValueToConstFunc(fv *full.FuncValue) interfaces.Func {
+	return &ConstFunc{
+		Value:    fv,
+		NameHint: "FuncValue",
+	}
+}
+
+func SimpleFnToDirectFunc(name string, fv *types.FuncValue) interfaces.Func {
+	return &simple.WrappedFunc{
+		Name: name,
+		Fn:   fv,
+	}
+}
+
+func SimpleFnToFuncValue(name string, fv *types.FuncValue) *full.FuncValue {
+	return &full.FuncValue{
+		V: func(txn interfaces.Txn, args []interfaces.Func) (interfaces.Func, error) {
+			wrappedFunc := SimpleFnToDirectFunc(name, fv)
+			txn.AddVertex(wrappedFunc)
+			for i, arg := range args {
+				argName := fv.T.Ord[i]
+				txn.AddEdge(arg, wrappedFunc, &interfaces.FuncEdge{
+					Args: []string{argName},
+				})
+			}
+			return wrappedFunc, nil
+		},
+		T: fv.T,
+	}
+}
+
+func SimpleFnToConstFunc(name string, fv *types.FuncValue) interfaces.Func {
+	return FuncValueToConstFunc(SimpleFnToFuncValue(name, fv))
+}