Fatal error: Call to undefined function get_currentuserinfo()

Please help me to resolve this error, I have temporally disabled mingle so the website works.

Fatal error: Call to undefined function get_currentuserinfo() in /home/parent/public_html/wp-content/plugins/mingle/classes/models/MnglUtils.php on line 291

287 /* PLUGGABLE FUNCTIONS AS TO NOT STEP ON OTHER PLUGINS’ CODE */
288 function get_currentuserinfo()
289 {
290 MnglUtils::_include_pluggables(‘get_currentuserinfo’);
291 return get_currentuserinfo();
292 }
293 function &get_userdata($id)
294 {
295 MnglUtils::_include_pluggables(‘get_userdata’);
296 return get_userdata($id);
297 }

function get_userdatabylogin($screenname)
{
MnglUtils::_include_pluggables(‘get_userdatabylogin’);
return get_userdatabylogin($screenname);
}

function wp_mail($recipient, $subject, $message, $header)
{
MnglUtils::_include_pluggables(‘wp_mail’);
return wp_mail($recipient, $subject, $message, $header);
}

function is_user_logged_in()
{
MnglUtils::_include_pluggables(‘is_user_logged_in’);
return is_user_logged_in();
}

function get_avatar( $id, $size )
{
MnglUtils::_include_pluggables(‘get_avatar’);
return get_avatar( $id, $size );
}

function wp_hash_password( $password_str )
{
MnglUtils::_include_pluggables(‘wp_hash_password’);
return wp_hash_password( $password_str );
}

function wp_generate_password( $length, $special_chars )
{
MnglUtils::_include_pluggables(‘wp_generate_password’);
return wp_generate_password( $length, $special_chars );
}

function wp_redirect( $location, $status=302 )
{
MnglUtils::_include_pluggables(‘wp_redirect’);
return wp_redirect( $location, $status );
}

function wp_salt( $scheme=’auth’ )
{
MnglUtils::_include_pluggables(‘wp_salt’);
return wp_salt( $scheme );
}

function _include_pluggables($function_name)
{
if(!function_exists($function_name))
require_once(ABSPATH . WPINC . ‘/pluggable.php’);
}
}
?>