helpers.go: two new functions: EvalStream() and EvalFile()

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
+}