Criteria built with the constructor functions (string(),
flag(), before(), sent_since(),
larger_than(), and their relatives) can be combined with the
native operators & (AND), | (OR), and ! (NOT),
as an alternative to AND and OR.
Precedence and grouping follow R's own rules, so parentheses work as
usual. See also ImapCon$query() for the expression-based
interface that does not require constructor calls at all.
Examples
if (FALSE) { # \dontrun{
con$search(string("budget", where = "SUBJECT") &
(sent_since(date_char = "01-Oct-2001") | !flag("SEEN")))
} # }
