modules are now represented by a struct that holds import-function, module description and importa status.

It is also available the new function IterateModules() to explore all modules.

func-base.go

@@ -55,5 +55,5 @@ func ImportBuiltinsFuncs(ctx ExprContext) {
 }
 
 func init() {
-	registerImport("builtins", ImportBuiltinsFuncs)
+	registerImport("base", ImportBuiltinsFuncs, "Base expression tools like isNil(), int(), etc.")
 }

func-import.go

@@ -142,5 +142,5 @@ func ImportImportFuncs(ctx ExprContext) {
 }
 
 func init() {
-	registerImport("import", ImportImportFuncs)
+	registerImport("import", ImportImportFuncs, "Functions import() and include()")
 }

func-math.go

@@ -115,5 +115,5 @@ func ImportMathFuncs(ctx ExprContext) {
 }
 
 func init() {
-	registerImport("math.arith", ImportMathFuncs)
+	registerImport("math.arith", ImportMathFuncs, "Function add() and mul()")
 }

func-os.go

@@ -164,5 +164,5 @@ func ImportOsFuncs(ctx ExprContext) {
 }
 
 func init() {
-	registerImport("os", ImportOsFuncs)
+	registerImport("os.file", ImportOsFuncs, "Operating system file functions")
 }

module-register.go

@@ -5,33 +5,49 @@
 package expr
 
 import (
+	"fmt"
 	"path/filepath"
 )
 
-var moduleRegister map[string]func(ExprContext)
+type module struct {
+	importFunc  func(ExprContext)
+	description string
+	imported    bool
+}
 
-func registerImport(name string, importFunc func(ExprContext)) {
+func newModule(importFunc func(ExprContext), description string) *module {
+	return &module{importFunc, description, false}
+}
+
+var moduleRegister map[string]*module
+
+func registerImport(name string, importFunc func(ExprContext), description string) {
 	if moduleRegister == nil {
-		moduleRegister = make(map[string]func(ExprContext))
+		moduleRegister = make(map[string]*module)
 	}
-	moduleRegister[name] = importFunc
+	if _, exists := moduleRegister[name]; exists {
+		panic(fmt.Errorf("module %q already registered", name))
+	}
+	moduleRegister[name] = newModule(importFunc, description)
 }
 
 func ImportInContext(ctx ExprContext, name string) (exists bool) {
-	var importFunc func(ExprContext)
+	var mod *module
-	if importFunc, exists = moduleRegister[name]; exists {
+	if mod, exists = moduleRegister[name]; exists {
-		importFunc(ctx)
+		mod.importFunc(ctx)
+		mod.imported = true
 	}
 	return
 }
 
 func ImportInContextByGlobPattern(ctx ExprContext, pattern string) (count int, err error) {
 	var matched bool
-	for name, importFunc := range moduleRegister {
+	for name, mod := range moduleRegister {
 		if matched, err = filepath.Match(pattern, name); err == nil {
 			if matched {
 				count++
-				importFunc(ctx)
+				mod.importFunc(ctx)
+				mod.imported = true
 			}
 		} else {
 			break
@@ -40,8 +56,19 @@ func ImportInContextByGlobPattern(ctx ExprContext, pattern string) (count int, e
 	return
 }
 
-func init() {
+func IterateModules(op func(name, description string, imported bool) bool) {
-	if moduleRegister == nil {
+	if op != nil {
-		moduleRegister = make(map[string]func(ExprContext))
+		for name, mod := range moduleRegister {
+			if !op(name, mod.description, mod.imported) {
+				break
+			}
+		}
+	}
+}
+
+// ----
+func init() {
+	if moduleRegister == nil {
+		moduleRegister = make(map[string]*module)
 	}
 }