merge: solved a lot of conflicts caused by an incorect commit removal

README.adoc

@@ -135,6 +135,9 @@ func main() {
 }
 ----
 
+=== Concepts and terminology
+#TODO#
+
 === Data types
 _Expr_ supports numerical, string, relational, boolean expressions, and mixed-type lists.
 
@@ -260,7 +263,15 @@ _Expr_ supports list of mixed-type values, also specified by normal expressions.
 |===
 
 === Variables
-#TODO: variables#
+A variable is an identifier with an assigned value. Variables are stored in the object that implements the _ExprContext_ interface.
+
+.Examples
+[source,go]
+----
+a=1
+x = 5.2 * (9-3)
+x = 1; y = 2*x
+----
 
 === Other operations
 
@@ -346,12 +357,15 @@ The table below shows all supported operators by decreasing priorities.
 .2+|*AND*| [blue]`and` | _Infix_ | _and_ | _boolean_ "and" _boolean_ -> _boolean_
 | [blue]`&&` | _Infix_ | _and_ | _boolean_ "&&" _boolean_ -> _boolean_
 .2+|*OR*| [blue]`or` | _Infix_ | _or_ | _boolean_ "or" _boolean_ -> _boolean_
-| [blue]`||` | _Infix_ | _or_ | _boolean_ "||" _boolean_ -> _boolean_
+| [blue]`\|\|` | _Infix_ | _or_ | _boolean_ "\|\|" _boolean_ -> _boolean_
 .1+|*ASSIGN*| [blue]`=` | _Infix_ | _assignment_ | _identifier_ "=" _any_ -> _any_
 .1+|*BUT*| [blue]`but` | _Infix_ | _but_ | _any_ "but" _any_ -> _any_
 |===
 
 === Functions
+Functions in _Expr_ are very similar to functions in many programming languages.
+
+In _Expr_ functions compute values in a local context (scope) that do not make effects on the calling context. This is the normal behavior. Using the reference operator [blue]`@` it is possibile to export local definition to the calling context.
 
 ==== Function calls
 #TODO: function calls operations#
@@ -359,8 +373,13 @@ The table below shows all supported operators by decreasing priorities.
 ==== Function definitions
 #TODO: function definitions operations#
 
-==== Builtins
+=== Builtins
 #TODO: builtins#
 
+==== Builtin functions
+
+==== [blue]_import()_
+[blue]_import([grey]#<source-file>#)_ loads the multi-expression contained in the specified source and returns its value.
+
 
 

ast.go

@@ -119,7 +119,7 @@ func (self *ast) eval(ctx ExprContext, preset bool) (result any, err error) {
 		if self.forest != nil {
 			for _, root := range self.forest {
 				if result, err = root.compute(ctx); err == nil {
-					ctx.SetVar(ControlLastResult, result)
+					ctx.setVar(ControlLastResult, result)
 				} else {
 					//err = fmt.Errorf("error in expression nr %d: %v", i+1, err)
 					break

context.go

@@ -33,6 +33,7 @@ type ExprContext interface {
 	Clone() ExprContext
 	GetVar(varName string) (value any, exists bool)
 	SetVar(varName string, value any)
+	setVar(varName string, value any)
 	EnumVars(func(name string) (accept bool)) (varNames []string)
 	EnumFuncs(func(name string) (accept bool)) (funcNames []string)
 	GetFuncInfo(name string) ExprFunc

operand-func.go

@@ -57,7 +57,7 @@ func exportVar(ctx ExprContext, name string, value any) {
 	if name[0] == '@' {
 		name = name[1:]
 	}
-	ctx.SetVar(name, value)
+	ctx.setVar(name, value)
 }
 
 func exportFunc(ctx ExprContext, name string, info ExprFunc) {
@@ -89,9 +89,9 @@ type funcDefFunctor struct {
 func (functor *funcDefFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
 	for i, p := range functor.params {
 		if i < len(args) {
-			ctx.SetVar(p, args[i])
+			ctx.setVar(p, args[i])
 		} else {
-			ctx.SetVar(p, nil)
+			ctx.setVar(p, nil)
 		}
 	}
 	result, err = functor.expr.eval(ctx, false)

operator-assign.go

@@ -31,7 +31,7 @@ func evalAssign(ctx ExprContext, self *term) (v any, err error) {
 		if functor, ok := v.(Functor); ok {
 			ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
 		} else {
-			ctx.SetVar(leftTerm.tk.source, v)
+			ctx.setVar(leftTerm.tk.source, v)
 		}
 	}
 	return

operator-coalesce.go

@@ -75,7 +75,7 @@ func evalAssignCoalesce(ctx ExprContext, self *term) (v any, err error) {
 			err = errCoalesceNoFunc(self.children[1])
 		} else {
 			v = rightValue
-			ctx.SetVar(leftTerm.source(), rightValue)
+			ctx.setVar(leftTerm.source(), rightValue)
 		}
 	}
 	return

simple-var-store.go

@@ -1,6 +1,8 @@
 // simple-var-store.go
 package expr
 
+import "fmt"
+
 type SimpleVarStore struct {
 	varStore map[string]any
 }
@@ -23,10 +25,18 @@ func (ctx *SimpleVarStore) GetVar(varName string) (v any, exists bool) {
 	return
 }
 
-func (ctx *SimpleVarStore) SetVar(varName string, value any) {
+func (ctx *SimpleVarStore) setVar(varName string, value any) {
 	ctx.varStore[varName] = value
 }
 
+func (ctx *SimpleVarStore) SetVar(varName string, value any) {
+	if allowedValue, ok := fromGenericAny(value); ok {
+		ctx.varStore[varName] = allowedValue
+	} else {
+		panic(fmt.Errorf("unsupported type %T of value %v", value, value))
+	}
+}
+
 func (ctx *SimpleVarStore) EnumVars(acceptor func(name string) (accept bool)) (varNames []string) {
 	varNames = make([]string, 0)
 	for name := range ctx.varStore {

utils.go

@@ -73,6 +73,8 @@ func anyInteger(v any) (i int64, ok bool) {
 		i = int64(intval)
 	case uint16:
 		i = int64(intval)
+	case uint64:
+		i = int64(intval)
 	case uint32:
 		i = int64(intval)
 	case int8:
@@ -89,6 +91,22 @@ func anyInteger(v any) (i int64, ok bool) {
 	return
 }
 
+func fromGenericAny(v any) (exprAny any, ok bool) {
+	if exprAny, ok = v.(bool); ok {
+		return
+	}
+	if exprAny, ok = v.(string); ok {
+		return
+	}
+	if exprAny, ok = anyInteger(v); ok {
+		return
+	}
+	if exprAny, ok = anyFloat(v); ok {
+		return
+	}
+	return
+}
+
 func anyFloat(v any) (float float64, ok bool) {
 	ok = true
 	switch floatval := v.(type) {