Question

I am trying to write a simple function that would bind to LDAP server and return a IO Bool value so that I can analyze the return in a conditional statement later.
This little snippet below works and prints an error if bind fails but it is not what I need.

import LDAP.Init
import LDAP.Exceptions

auth :: IO ()
auth = do
  c <- ldapOpen "10.1.1.11" 3268
  let bnd =ldapSimpleBind c "[e-mail]" "mypassword"
  catchLDAP bnd (\_ -> error "Wrong user name or password")

I get an error if I try to return anything but IO () by the function that deals with exception. I need it to return IO Bool.

‘ldapSimpleBind’ just throws an exception if unsuccessful and that’s all. Catching exceptions will only allow me to return an IO ()
What I need is to return something meaningful so that I can do something useful with the return value.
I am clearly missing something as the signature of catchLDAP in the docs is :: IO a -> (LDAPException -> IO a) -> IO a

What am I doing wrong?
Thanks.

Answer 1

Your bnd action doesn’t return true when it succeeds, and the error handler just calls error,

So it seems that you could just let bnd' = bnd >> return true ,

then, catchLDAP bnd' $ \_ -> return false.