How to use function

To see how to grant privileges on user-defined extension (UDx) to users and roles read this: https://www.vertica.com/docs/10.0.x/HTML/Content/Authoring/SQLReferenceManual/Statements/GRANT/GRANTUserDefinedExtension.htm
Please also verify that the granted user session include a PATH to your function Schema:
SHOW SEARCH_PATH;
And if needed: SET SEARCH_PATH to YOUR_FUNCTION_SCHEMA_NAME, public;

Thank you for an immediate answer.
Run the following command to make sure that user-defined functions are available to the general user.
@dbadmin
create fuction test_func() return date as begin ...end;
grant execute on function test_func() to public;
@general user
select test_func();
That's all, thank you.