diff --git a/cmd/pgen/gen.go b/cmd/pgen/gen.go
index cf83c10..e2e9776 100644
--- a/cmd/pgen/gen.go
+++ b/cmd/pgen/gen.go
@@ -16,15 +16,13 @@ type subspec struct {
 	s string
 }
 
-var (
+type Generator struct{
 	firstone bool
-	gfset *token.FileSet
+	fset *token.FileSet
 	fspec, tspec, nspec subspec
-	ntspecs []subspec
+	nspecs []subspec
 	nodes *ast.File
-)
-
-type gvisit struct{}
+}
 
 func subs(dst *string, specs []subspec) {
 	for _,spec := range(specs) {
@@ -38,79 +36,81 @@ func sub(dst *string,spec subspec) {
 	}
 }
 
-func (v *gvisit) Visit(node ast.Node) ast.Visitor {
+func (g *Generator) Visit(node ast.Node) ast.Visitor {
 	switch n := node.(type) {
 	case *ast.Ident:
 		if n.Obj != nil && n.Obj.Kind == ast.Typ {
-			subs(&n.Name,ntspecs)
-			subs(&n.Obj.Name,ntspecs)
+			subs(&n.Name,g.nspecs)
+			subs(&n.Obj.Name,g.nspecs)
 		}
 	case *ast.TypeSwitchStmt:
 		for _,s := range(n.Body.List) {
 			cs, ok := s.(*ast.CaseClause); if !ok { continue }
 			for _,c := range(cs.List) {
 				ci, ok := c.(*ast.Ident); if !ok { continue }
-				subs(&ci.Name,ntspecs)
+				subs(&ci.Name,g.nspecs)
 			}
 		}
 	case *ast.TypeAssertExpr:
-		nt, ok := n.Type.(*ast.Ident); if !ok { return v }
-		subs(&nt.Name,ntspecs)
+		nt, ok := n.Type.(*ast.Ident); if !ok { return g }
+		subs(&nt.Name,g.nspecs)
 	case *ast.Ellipsis:
-		nt, ok := n.Elt.(*ast.Ident); if !ok { return v }
-		subs(&nt.Name,ntspecs)
+		nt, ok := n.Elt.(*ast.Ident); if !ok { return g }
+		subs(&nt.Name,g.nspecs)
 	case *ast.Field:
-		nt, ok := n.Type.(*ast.Ident); if !ok { return v }
-		subs(&nt.Name,ntspecs)
+		nt, ok := n.Type.(*ast.Ident); if !ok { return g }
+		subs(&nt.Name,g.nspecs)
 	case *ast.StarExpr:
-		nt, ok := n.X.(*ast.Ident); if !ok { return v }
-		subs(&nt.Name,ntspecs)
-	case *ast.TypeSpec:
-		//ast.Print(gfset,n)
+		nt, ok := n.X.(*ast.Ident); if !ok { return g }
+		subs(&nt.Name,g.nspecs)
 	case *ast.ValueSpec:
-		nt, ok := n.Type.(*ast.Ident); if !ok { return v }
-		subs(&nt.Name,ntspecs)
+		nt, ok := n.Type.(*ast.Ident); if !ok { return g }
+		subs(&nt.Name,g.nspecs)
 	case *ast.ArrayType:
-		nt, ok := n.Elt.(*ast.Ident); if !ok { return v }
-		subs(&nt.Name,ntspecs)
+		nt, ok := n.Elt.(*ast.Ident); if !ok { return g }
+		subs(&nt.Name,g.nspecs)
 	case *ast.MapType:
 		nt, ok := n.Key.(*ast.Ident); if ok {
-			subs(&nt.Name,ntspecs)
+			subs(&nt.Name,g.nspecs)
 		}
 		nt, ok = n.Value.(*ast.Ident); if ok {
-			subs(&nt.Name,ntspecs)
+			subs(&nt.Name,g.nspecs)
 		}
 	case *ast.FuncDecl:
-		sub(&n.Name.Name,fspec)
-		//ast.Print(gfset,n)
+		sub(&n.Name.Name,g.fspec)
+		//ast.Print(g.fset,n)
 	}
-	return v
+	return g
 }
 
 func init() {
-	firstone = true
 	err := os.Remove("pgen.go")
 	if err != nil && os.IsExist(err) {
 		log.Fatal("Removing pgen.go:",err)
 	}
 }
 
-func add(newName, typName, typ string) {
-	fspec = subspec{regexp.MustCompile("New"), newName}
-	nspec = subspec{regexp.MustCompile("_N"), typName}
-	tspec = subspec{regexp.MustCompile("_T"), typ}
-	ntspecs = []subspec{nspec,tspec}
+func NewGenerator() *Generator {
+	g := &Generator{}
+	g.firstone = true
+	g.fset = token.NewFileSet()
+	return g
+}
 
-	gfset = token.NewFileSet()
-	f, err := parser.ParseFile(gfset, "", template, 0)
+func (g *Generator) Add(newName, typName, typ string) {
+	g.fspec = subspec{regexp.MustCompile("New"), newName}
+	g.nspecs = []subspec{
+		subspec{regexp.MustCompile("_N"), typName},
+		subspec{regexp.MustCompile("_T"), typ}}
+
+	f, err := parser.ParseFile(g.fset, "", template, 0)
 	if err != nil {
 		log.Fatal("Parsing persist/template.T:",err)
 	}
-	var v = &gvisit{}
-	ast.Walk(v,f)
+	ast.Walk(g,f)
 
-	if firstone {
-		nodes = f
+	if g.firstone {
+		g.nodes = f
 	} else {
 		for _,decl := range(f.Decls) {
 			imp, ok := decl.(*ast.GenDecl); if ok {
@@ -118,20 +118,27 @@ func add(newName, typName, typ string) {
 					continue // skip imports
 				}
 			}
-			nodes.Decls = append(nodes.Decls,decl)
+			g.nodes.Decls = append(g.nodes.Decls,decl)
 		}
 	}
-	firstone = false
+	g.firstone = false
 }
 
-func newImportSpec(name string) *ast.ImportSpec {
-	path := &ast.BasicLit{ Value: name }
-	ret := &ast.ImportSpec{ Path: path }
-	return ret
+func (g *Generator) Import(imports map[string]bool) {
+	if g.nodes == nil {
+		return
+	}
+
+	// strip quotation marks from imports
+	qexp := regexp.MustCompile(`"`)
+	for v := range imports {
+		v = qexp.ReplaceAllString(v,"")
+		astutil.AddImport(g.fset, g.nodes, v)
+	}
 }
 
-func gen(wantImps []string) {
-	if nodes == nil {
+func (g *Generator) Save() {
+	if g.nodes == nil {
 		return
 	}
 	of, err := os.Create("pgen.go")
@@ -139,13 +146,7 @@ func gen(wantImps []string) {
 		log.Fatal("Cannot open pgen.go")
 	}
 
-	qexp := regexp.MustCompile(`"`)
-	for _,v := range wantImps {
-		v = qexp.ReplaceAllString(v,"")
-		astutil.AddImport(gfset, nodes, v)
-	}
-
-	err = format.Node(of,gfset,nodes)
+	err = format.Node(of,g.fset,g.nodes)
 	if err != nil {
 		log.Fatal("Generate error:",err)
 	}
diff --git a/cmd/pgen/main.go b/cmd/pgen/main.go
index 0aa5a47..5561a5e 100644
--- a/cmd/pgen/main.go
+++ b/cmd/pgen/main.go
@@ -103,30 +103,26 @@ func init() {
 
 	imps = make(map[string]string)
 	needImps = make(map[string]bool)
-	ts = make(map[string]tps)
 	fset = token.NewFileSet()
 }
 
 func main() {
-	// In naming imported identifiers, keep only the last part of the
-	// path to the imported package. This does not take named imports
-	// into account but should allow the code generator to find the
-	// right libary to import and generate valid code.
-
 	pkgs, err := parser.ParseDir(fset, ".", nil, 0)
 	if err != nil {
 		log.Fatal("Parse:",err)
 	}
+	// run type checker on each package
 	for _,pkg := range pkgs {
+		ts = make(map[string]tps)
 		chkpkg(pkg)
+		g := NewGenerator()
+		for _,v := range ts {
+			g.Add(v.fun, v.name, v.typ)
+		}
+		g.Import(needImps)
+		// process template for each type identified and
+		// generate output
+		g.Save()
 	}
-	addImps := make([]string,0)
-	for k := range needImps {
-		addImps = append(addImps,imps[k])
-	}
-	for _,v := range ts {
-		add(v.fun, v.name, v.typ)
-	}
-	gen(addImps)
 }