New ScanExt() function allowing the introductory character to be chosen

expander-context.go

@@ -10,8 +10,6 @@ import (
 	"git.portale-stac.it/go-pkg/golang"
 )
 
-const varIntro = '$'
-
 type ExpanderFunc func(ctx ExpanderContext, varValue string, args []string) (result string, err error)
 
 type ExpanderFuncBlock struct {

scanner.go

@@ -17,11 +17,18 @@ const (
 // Flags symbols in the abova iota order
 const flagSymbols = "!=*"
 
+const defaultVarIntro = '$'
+
+
 type VariableHandler interface {
 	Handle(varSpec string, flags ScannerFlag) (value string, err error)
 }
 
 func Scan(handler VariableHandler, source string) (result string, err error) {
+	return ScanExt(defaultVarIntro, handler, source)
+}
+
+func ScanExt(varIntro byte,  handler VariableHandler, source string) (result string, err error) {
 	var spec, value string
 	var flags ScannerFlag
 	var backSlash bool

utils.go

@@ -6,5 +6,5 @@ import (
 )
 
 func Var(name string) string {
-	return fmt.Sprintf("%c{%s}", varIntro, name)
+	return fmt.Sprintf("%c{%s}", defaultVarIntro, name)
 }