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.

data-cursor.go

@@ -5,11 +5,14 @@
 package expr
 
 import (
+	"errors"
 	"io"
 )
 
 const (
 	initName    = "init"
+	cleanName   = "clean"
+	resetName   = "reset"
 	nextName    = "next"
 	currentName = "current"
 )
@@ -20,6 +23,8 @@ type dataCursor struct {
 	index       int
 	resource    any
 	nextFunc    Functor
+	cleanFunc   Functor
+	resetFunc   Functor
 	currentFunc Functor
 }
 
@@ -35,6 +40,30 @@ func (dc *dataCursor) String() string {
 	return "$(...)"
 }
 
+func (dc *dataCursor) Reset() (err error) {
+	if dc.resetFunc != nil {
+		ctx := cloneContext(dc.ctx)
+		if _, err = dc.resetFunc.Invoke(ctx, resetName, []any{}); err == nil {
+			dc.index = -1
+		}
+		exportObjects(dc.ctx, ctx)
+	} else {
+		err = errors.New("no 'reset' function defined in the data-source")
+	}
+	return
+}
+
+func (dc *dataCursor) Clean() (err error) {
+	if dc.cleanFunc != nil {
+		ctx := cloneContext(dc.ctx)
+		_, err = dc.cleanFunc.Invoke(ctx, cleanName, []any{})
+		exportObjects(dc.ctx, ctx)
+	} else {
+		err = errors.New("no 'clean' function defined in the data-source")
+	}
+	return
+}
+
 func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
 	ctx := cloneContext(dc.ctx)
 	if item, err = dc.currentFunc.Invoke(ctx, currentName, []any{}); err == nil && item == nil {

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")
 }

function-register.go

@@ -1,47 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// function-register.go
-package expr
-
-import (
-	"path/filepath"
-)
-
-var functionRegister map[string]func(ExprContext)
-
-func registerImport(name string, importFunc func(ExprContext)) {
-	if functionRegister == nil {
-		functionRegister = make(map[string]func(ExprContext))
-	}
-	functionRegister[name] = importFunc
-}
-
-func ImportInContext(ctx ExprContext, name string) (exists bool) {
-	var importFunc func(ExprContext)
-	if importFunc, exists = functionRegister[name]; exists {
-		importFunc(ctx)
-	}
-	return
-}
-
-func ImportInContextByGlobPattern(ctx ExprContext, pattern string) (count int, err error) {
-	var matched bool
-	for name, importFunc := range functionRegister {
-		if matched, err = filepath.Match(pattern, name); err == nil {
-			if matched {
-				count++
-				importFunc(ctx)
-			}
-		} else {
-			break
-		}
-	}
-	return
-}
-
-func init() {
-	if functionRegister == nil {
-		functionRegister = make(map[string]func(ExprContext))
-	}
-}

helpers.go

@@ -6,6 +6,8 @@ package expr
 
 import (
 	"fmt"
+	"io"
+	"os"
 	"strings"
 )
 
@@ -59,3 +61,24 @@ func EvalStringV(source string, args []Arg) (result any, err error) {
 	}
 	return
 }
+
+func EvalStream(ctx ExprContext, r io.Reader) (result any, err error) {
+	var tree *ast
+	scanner := NewScanner(r, DefaultTranslations())
+	parser := NewParser(ctx)
+
+	if tree, err = parser.Parse(scanner); err == nil {
+		result, err = tree.Eval(ctx)
+	}
+	return
+}
+
+func EvalFile(ctx ExprContext, filePath string) (result any, err error) {
+	var fh *os.File
+	if fh, err = os.Open(filePath); err != nil {
+		return nil, err
+	}
+	defer fh.Close()
+	result, err = EvalStream(ctx, fh)
+	return
+}

module-register.go

@@ -0,0 +1,74 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// module-register.go
+package expr
+
+import (
+	"fmt"
+	"path/filepath"
+)
+
+type module struct {
+	importFunc  func(ExprContext)
+	description string
+	imported    bool
+}
+
+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]*module)
+	}
+	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 mod *module
+	if mod, exists = moduleRegister[name]; exists {
+		mod.importFunc(ctx)
+		mod.imported = true
+	}
+	return
+}
+
+func ImportInContextByGlobPattern(ctx ExprContext, pattern string) (count int, err error) {
+	var matched bool
+	for name, mod := range moduleRegister {
+		if matched, err = filepath.Match(pattern, name); err == nil {
+			if matched {
+				count++
+				mod.importFunc(ctx)
+				mod.imported = true
+			}
+		} else {
+			break
+		}
+	}
+	return
+}
+
+func IterateModules(op func(name, description string, imported bool) bool) {
+	if op != nil {
+		for name, mod := range moduleRegister {
+			if !op(name, mod.description, mod.imported) {
+				break
+			}
+		}
+	}
+}
+
+// ----
+func init() {
+	if moduleRegister == nil {
+		moduleRegister = make(map[string]*module)
+	}
+}

operand-iterator.go

@@ -54,14 +54,23 @@ func getDataSourceDict(ctx ExprContext, self *term) (ds map[string]Functor, err
 
 	if dictAny, ok := value.(map[any]any); ok {
 		ds = make(map[string]Functor)
-		for _, k := range []string{initName, currentName, nextName} {
+		// required functions
+		for _, k := range []string{currentName, nextName} {
 			if item, exists := dictAny[k]; exists && item != nil {
 				if functor, ok := item.(*funcDefFunctor); ok {
 					ds[k] = functor
 				}
-			} else if k != initName {
+			} else {
 				err = fmt.Errorf("the data-source must provide a non-nil %q operator", k)
-				break
+				return
+			}
+		}
+		// Optional functions
+		for _, k := range []string{initName, resetName, cleanName} {
+			if item, exists := dictAny[k]; exists && item != nil {
+				if functor, ok := item.(*funcDefFunctor); ok {
+					ds[k] = functor
+				}
 			}
 		}
 	} else {
@@ -98,6 +107,9 @@ func evalIterator(ctx ExprContext, self *term) (v any, err error) {
 
 	dc.nextFunc, _ = ds[nextName]
 	dc.currentFunc, _ = ds[currentName]
+	dc.cleanFunc, _ = ds[cleanName]
+	dc.resetFunc, _ = ds[resetName]
+
 	v = dc
 
 	return

operator-builtin.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// operator-length.go
+// operator-builtin.go
 package expr
 
 //-------- builtin term

operator-dot.go

@@ -17,50 +17,67 @@ func newDotTerm(tk *Token) (inst *term) {
 	}
 }
 
+func verifyIndex(ctx ExprContext, indexTerm *term, maxValue int) (index int, err error) {
+	var v int
+	var indexValue any
+	if indexValue, err = indexTerm.compute(ctx); err == nil {
+		if v, err = indexTerm.toInt(indexValue, "index expression value must be integer"); err == nil {
+			if v >= 0 && v < maxValue {
+				index = v
+			} else if index >= -maxValue {
+				index = maxValue + v
+			} else {
+				err = indexTerm.Errorf("index %d out of bounds", v)
+			}
+		}
+	}
+	return
+}
+
 func evalDot(ctx ExprContext, self *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if err = self.checkOperands(); err != nil {
+		return
+	}
+	if leftValue, err = self.children[0].compute(ctx); err != nil {
 		return
 	}
 
 	indexTerm := self.children[1]
 
-	if isList(leftValue) {
+	switch unboxedValue := leftValue.(type) {
+	case []any:
 		var index int
-		if index, err = indexTerm.toInt(rightValue, "index expression value must be integer"); err != nil {
-			return
+		if index, err = verifyIndex(ctx, indexTerm, len(unboxedValue)); err == nil {
+			v = unboxedValue[index]
 		}
-
-		list, _ := leftValue.([]any)
-		if index >= 0 && index < len(list) {
-			v = list[index]
-		} else if index >= -len(list) {
-			v = list[len(list)+index]
-		} else {
-			err = indexTerm.Errorf("index %v out of bounds", index)
-		}
-	} else if isString(leftValue) {
+	case string:
 		var index int
-		if index, err = indexTerm.toInt(rightValue, "index expression value must be integer"); err != nil {
-			return
+		if index, err = verifyIndex(ctx, indexTerm, len(unboxedValue)); err == nil {
+			v = unboxedValue[index]
 		}
-
-		s, _ := leftValue.(string)
-		if index >= 0 && index < len(s) {
-			v = string(s[index])
-		} else if index >= -len(s) {
-			v = string(s[len(s)+index])
-		} else {
-			err = indexTerm.Errorf("index %v out of bounds", index)
-		}
-	} else if isDict(leftValue) {
+	case map[any]any:
 		var ok bool
-		d, _ := leftValue.(map[any]any)
-		if v, ok = d[rightValue]; !ok {
-			err = fmt.Errorf("key %v does not belong to the dictionary", rightValue)
+		var indexValue any
+		if indexValue, err = indexTerm.compute(ctx); err == nil {
+			if v, ok = unboxedValue[indexValue]; !ok {
+				err = fmt.Errorf("key %v does not belong to the dictionary", rightValue)
+			}
 		}
-	} else {
+	case *dataCursor:
+		if indexTerm.symbol() == SymIdentifier {
+			opName := indexTerm.source()
+			if opName == resetName {
+				err = unboxedValue.Reset()
+			} else if opName == cleanName {
+				err = unboxedValue.Clean()
+			} else {
+				err = indexTerm.Errorf("iterators do not support command %q", opName)
+			}
+			v = err == nil
+		}
+	default:
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return

operator-include.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-include.go
+package expr
+
+//-------- include term
+
+func newIncludeTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priSign,
+		evalFunc: evalInclude,
+	}
+}
+
+func evalInclude(ctx ExprContext, self *term) (v any, err error) {
+	var childValue any
+
+	if childValue, err = self.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	count := 0
+	if isList(childValue) {
+		list, _ := childValue.([]any)
+		for i, filePathSpec := range list {
+			if filePath, ok := filePathSpec.(string); ok {
+				if v, err = EvalFile(ctx, filePath); err == nil {
+					count++
+				} else {
+					err = self.Errorf("can't load file %q", filePath)
+					break
+				}
+			} else {
+				err = self.Errorf("expected string at item nr %d, got %T", i+1, filePathSpec)
+				break
+			}
+		}
+	} else if isString(childValue) {
+		filePath, _ := childValue.(string)
+		v, err = EvalFile(ctx, filePath)
+	} else {
+		err = self.errIncompatibleType(childValue)
+	}
+	if err == nil {
+		v = count
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwInclude, newIncludeTerm)
+}

operator-length.go

@@ -25,12 +25,12 @@ func evalLength(ctx ExprContext, self *term) (v any, err error) {
 
 	if isList(rightValue) {
 		list, _ := rightValue.([]any)
-		v = len(list)
+		v = int64(len(list))
 	} else if isString(rightValue) {
 		s, _ := rightValue.(string)
-		v = len(s)
+		v = int64(len(s))
 	} else if it, ok := rightValue.(Iterator); ok {
-		v = it.Index()
+		v = int64(it.Index())
 	} else {
 		err = self.errIncompatibleType(rightValue)
 	}

symbol.go

@@ -33,7 +33,7 @@ const (
 	SymBackTick                          //  22: '`'
 	SymExclamation                       //  23: '!'
 	SymQuestion                          //  24: '?'
-	SymAmpersand                         //  25: '&&'
+	SymAmpersand                         //  25: '&'
 	SymDoubleAmpersand                   //  26: '&&'
 	SymPercent                           //  27: '%'
 	SymAt                                //  28: '@'
@@ -64,7 +64,7 @@ const (
 	SymCaret                             //  53: '^'
 	SymDollarRound                       //  54: '$('
 	SymOpenClosedRound                   //  55: '()'
-	SymDoubleDollar                      //  56: '$$
+	SymDoubleDollar                      //  56: '$$'
 	SymChangeSign
 	SymUnchangeSign
 	SymIdentifier
@@ -96,6 +96,7 @@ const (
 	SymKwBut
 	SymKwFunc
 	SymKwBuiltin
+	SymKwInclude
 	SymKwNil
 )
 
@@ -108,6 +109,7 @@ func init() {
 		"BUILTIN": SymKwBuiltin,
 		"BUT":     SymKwBut,
 		"FUNC":    SymKwFunc,
+		"INCLUDE": SymKwInclude,
 		"NOT":     SymKwNot,
 		"OR":      SymKwOr,
 		"NIL":     SymKwNil,

term.go

@@ -217,9 +217,9 @@ func (self *term) evalInfix(ctx ExprContext) (leftValue, rightValue any, err err
 	return
 }
 
-func (self *term) evalPrefix(ctx ExprContext) (rightValue any, err error) {
+func (self *term) evalPrefix(ctx ExprContext) (childValue any, err error) {
 	if err = self.checkOperands(); err == nil {
-		rightValue, err = self.children[0].compute(ctx)
+		childValue, err = self.children[0].compute(ctx)
 	}
 	return
 }