func Upper(_ context.Context, args ...core.Value) (core.Value, error) {
	err := core.ValidateArgs(args, 1, 1)
	if err != nil {
		return values.EmptyString, err
	}
	text := strings.ToUpper(args[0].String())
	return values.NewString(text), nil
}
Upper converts strings to their upper-case counterparts. All other characters are returned unchanged.
@param src (String) - The source string.
@returns (String) - THis string in upper case.
package strings
import (
	"context"
	"strings"
	"github.com/MontFerret/ferret/pkg/runtime/core"
	"github.com/MontFerret/ferret/pkg/runtime/values"
)
func Lower(_ context.Context, args ...core.Value) (core.Value, error) {
	err := core.ValidateArgs(args, 1, 1)
	if err != nil {
		return values.EmptyString, err
	}
	text := strings.ToLower(args[0].String())
	return values.NewString(text), nil
}